We just hotfixed the following changes to the Trial of the Grand Crusader (aka Heroic mode).

Northrend Beasts

• Fixed a bug where the flag that prevents a creature from gaining attack speed after a parry was inadvertently left off Gormok the Impaler. This bug is fixed in normal mode as well.
• Increased the amount of time players have to defeat the encounter before Icehowl berserks.
• You have an extra half second to get out of the way of a very angry charging Yeti. Players with high ping rejoice.
• Icehowl will become tauntable. (This particular element isn't hotfixed quite yet, but should be shortly).

Lord Jaraxxus

• Infernal Eruption will now spawn an additional Felflame Infernal the instant the eruption occurs.
• Nether Portal now summons Mistresses of Pain slightly more often.