[Happyfeet]

As I understand it:
DS's on anyone are neutral damage, including your pet. The reason you didn't get XP for the 2nd mob is because you failed to do 1 dmg to it. So if you had hit each mob for 1, you'd get both xp's. Now whether you out damage your pet is another question. You'd have to do more damage than him on both to receive full XP.

Edit: ya what Drav said, I typed that out like 2 hours ago then forgot to hit reply lol.