Today’s Wrath Classic hotfixes address pet attack issues, mostly related to DKs, as well as a Paladin problem related to DKs as well.
February 9 (Source)
Wrath of the Lich King Classic
Fixed a bug that could prevent combat pets from attacking when the player attacks.
Developers’ notes: This bug was commonly seen by Death Knights, who reported their Army of the Dead ghouls standing around when they were expected to be attacking the Death Knight’s target. As a result of this fix, all combat pets should now engage enemies as they did in original Wrath of the Lich King. Now, pets in Defensive mode will attack when you do, without requiring that you command them to attack, and pets that don’t come with a pet bar will default to Defensive mode.
Fixed an issue causing Paladins’ Improved Concentration Aura to reduce the duration of friendly Death Knights’ Anti-Magic Shell.