Correct me if I'm wrong, but the addition of pets in PvP somehow increases the occurrences of lag. Perhaps it's because of the additional visual clutter due to rendering of pets.

BTW, do pets level up when used in PvP? Hope this is true, because their happiness gauge goes down when using them in PvP.

IMHO (thus far), pets are just a nuisance in PvP, even though we are benefiting from their presence. But it's just my opinion.