Class balance based on PTR Testing (Source)
The PTR does not exist solely for balance feedback. They provide crash reports, bug reports, having the patches simply live on a test environment with people actively playing helps us catch a great number of issues that no one would even need post about. Beyond that though the bug reports that are posted are extremely helpful, and overall the PTRs lead without a doubt to a more stable patch than it would have been were there no public test.

In direct answer to what you're referring, unless there's new content, the number of people on the PTR is really pretty low. Too low to pull reliable metrics to base balance changes on. Unless there's new content to drive people to the PTR there generally just isn't a sample size. Which is fine, because we can make changes after the PTR once the patch hits the live realms. Issuing hotfixes after a patch is by no means something new. We've used hotfixes for quite a long time, but since Cataclysm and the new community site, hotfix changes are front page news through the blogs. Which is awesome. Before we were throwing out pretty much the same amount of hotfixes we were after 4.0.6. Difference being we didn't have a great way to tell anyone about them. So now hotfixes are very visible and it makes it seem like we're going crazy with them, when really it's just increased transparency into the changes we're making.

Going back to your question, the PTR does many great things for the patches, and it should be expected that we're not going to make balance changes based on forum posts alone. The designers don't believe their own play experience is reason enough to make balance changes, although it can be one part of the puzzle, and the same goes for us reading about yours.  

Here you'll find a list of hotfixes that address various issues related to the recently released World of Warcraft: Cataclysm patch 4.0.6. Hotfixes are updates we make on our end without requiring you to download a new patch. Some of the hotfixes below will go live the moment they are implemented, while others may require your realm to be restarted to go into effect. Please keep in mind that some issues cannot be addressed without a client-side patch update. We will continue to update this thread in the days ahead as additional hotfixes are applied. Visit our Bug Report forum for a list of 4.0.6 known issues.

February 18
Battlegrounds

• Demolishers were respawning too quickly in Strand of the Ancients. They are now on a 20-second spawn timer.

• Death knight Ghouls under the effects of Dark Transformation can no longer cast Gnaw while it's on cooldown.

Hunter

• Aimed Shot damage has been decreased to approximately 160% weapon damage (at level 80+), down from 200%.
• Aspect of the Hawk now provides around an additional 2000 attack power at level 85.

Paladin

• Light of Dawn no longer heals targets outside the paladin's party or raid. It correctly heals up to 5 targets in the paladin's raid.

Priest

• Body and Soul no longer reduces the mana cost of Power Word: Shield (the hotfix made on February 16 to provide this additional benefit has been reverted).
• Rapture now returns 2/5/7% of maximum mana when Power Word: Shield is consumed, up from 2/4/6%.

Warlock

• Instant-cast Shadowbolts from Shadow Trance (both the talent and Glyph of Corruption versions) should no longer consume charges of Backdraft if both procs are available. Shadow Trance will always take priority and be consumed first when Backdraft is active. Subsequent Shadowbolts will consume Backdraft stacks.

Warrior

• Two-Handed Weapon Specialization (Arms passive) now gives 20% bonus damage with two-handed weapons, up from 10%.

Dungeon Finder

• If a party member remains outside of a dungeon for more than 3 minutes, they become eligible for removal, regardless of other Vote Kick restrictions.
• When players queue as a group with a tank or a healer, and the tank or healer drops group (or is kicked) within the first 5 minutes, all of the other players who queued with them are removed from the group as well.
• If there is a group of 3 or more friends and someone in that group initiates a Vote Kick of a random party member, it now requires 4 votes to kick the player, instead of the standard 3 votes.
• The penalty for using the Vote Kick feature too often is not issued to a player who kicks someone with whom they queued for a dungeon (i.e. the party member being selected for removal is not a player randomly selected via the Dungeon Finder).
• The penalty for using the Vote Kick feature too often will be issued much more quickly to players who join as a party of 4 and kick the randomly selected 5th player.
• The penalty for using the Vote Kick feature too often will now not allow the player to initiate a Vote Kick for 2 hours, up from 45 minutes.
• These changes will require realm restarts to take effect. More information can be found here.

Dungeons & Raids

• When switching a normal raid dungeon over to Heroic difficulty, players were instantly becoming saved without warning. There is now a warning dialog box which will appear before the difficulty is changed.

Today's Hotfixes (Source)
We actually spent a bit of time talking to the designers about this very topic, and it's something they're well aware of and realize isn't always ideal.

A few really great points came out of that meeting, though:

• Some changes in 4.0.6 and/or 4.0.6a were just wrong. For a myriad of reasons the changes made in 4.0.6/4.0.6a either did not pan out as expected, or were simply mis-calculations/interpretations. Which is the reason for a number of the quick reversions and changes in hotfixes shortly after the patch.
  
  
• While there was feedback from the PTR on what is broken, overpowered, underpowered, etc. there simply wasn't enough data and real world proof for us to make changes. Forum posts always make a lot of noise. It's difficult to separate the seed from the chaff. Yes, it turned out a number of reports proved to be accurate once the 4.0.6's hit the masses and we were able to get a sample size that showed us what needed adjusting.
  
  
• The third point discussed was that we have an obligation to deploy hotfixes when we feel we're making quality of life-improvements, fixing errors, or simply making good balance changes. Good balance is very much debatable among who you ask, of course. ;)
  
  
• Fourth point really struck home with all of the designers, and that's that they also have an obligation to not use the live realms as a balancing laboratory. That while the changes being made have seemed very quick and sporadic at times, that there is thought and planning going in to them, and they are consciously avoiding throwing out changes and seeing what happens. While some changes have been implemented and then reverted, it's not because a lot of thought and effort didn't go into them, but that simply they didn't work as intended.

I know a lot of us remember the old days where classes would sit without changes for months, in some cases years for specific mechanics. A class would dominate for 6 months, and that's just how the game was. While we think good, measured changes in patches is far more visible and understandable, that hotfixes allow so much more to offering immediate relief that we'd be remiss in not using them to offer a better game experience to you, the players. There's an agreement that 4.0.6 and 4.0.6a have been pretty chaotic with hotfixes, and that's due to a number of issues that we don't consider to be 'usual'. We fully expect them to slow down substantially from this point, and we really appreciate everyone who stays on top of the hotfix blog, and relates the changes as they're made to their guildies and friends. 

King Varian Wrynn, Queen Sylvanas Windrunner, King Genn Greymane, and Trade Prince Gallywix -- these are just a few of the leaders who continue to shape Azeroth's destiny. They embody their races' strongest traits... and at times their greatest failings. The Leaders of the Horde and Alliance is a series of short stories from Blizzard Entertainment that peer into the hearts of these legendary heroes and offer insight into what new trials might lie ahead as they lead their people in a world forever changed by the Cataclysm.

"Trade Secrets of a Trade Prince," the third story in this series, takes us on a journey into the mind of Gallywix, one of the goblins' most exceptionally shrewd movers and shakers. Becoming a Trade Prince doesn't just happen overnight, and you certainly don't get your likeness carved into the side of a mountain by letting others push you around and take what's yours.

So read on and learn the tricks of the trade that led Gallywix to untold fortune and success, and maybe one day you, too, can be a powerful and renowned goblin just like him.

Ha. Right.

Here you'll find a list of hotfixes that address various issues related to the recently released World of Warcraft: Cataclysm patch 4.0.6. Hotfixes are updates we make on our end without requiring you to download a new patch. Some of the hotfixes below will go live the moment they are implemented, while others may require your realm to be restarted to go into effect. Please keep in mind that some issues cannot be addressed without a client-side patch update. We will continue to update this thread in the days ahead as additional hotfixes are applied. Visit our Bug Report forum for a list of 4.0.6 known issues.

February 16
Druid

• It is no longer possible for Skull Bash (Bear) to hit two targets at a time. A macro was previously circumventing the intended functionality of this ability.

Shaman

• Purification (Restoration passive) now grants a 25% bonus to healing effects, up from 10%. More information can be found here.

Priest

• In addition to its current effects, the Body and Soul talent now grants 12.5%/25% reduction to the base mana cost of Power Word: Shield. This is not reflected in the tooltip, but is reflected in the amount of mana used when Power Word: Shield is cast by Holy priests who have this talent. The tooltip update will require a client-side patch.
• Power Word: Shield now costs roughly 34% of base mana, up from 25%. This is not reflected in the tooltip, but is reflected in the amount of mana used when the spell is cast. The tooltip update will require a client-side patch.
• More information on these changes can be found here.

Dungeons & Raids
Blackwing Descent

• Maloriak will no longer cast Flash Freeze on anyone who is tanking Aberrations or anyone who has recently been hit by them.