Sooo... Having a pet, makes you lose loot??

[Deleted]

From my years of experience, a player only needs to do 1 damage in order to be eligible for getting the loot and the pet can do the rest.
While if it's a npc (guard, neutral sentry) you need to make sure a certain percent of damage is done by the player in order to claim the loot from it.

Blizzards way to prevent their own game features from contributing to automated game play.

[imotion]

Some bosses, like conclave of wind is still buggy and will not reward loot if your pet gets the killing blow.

[nToxik]

This was changed by Blizzard either during TBC or the start of Lich King. Prior to that, you could get loot if your pet solo'd an npc with no damage from you. Blizzard changed it so that you could not use only your pet to farm loot.