As the title says, there is a bug when you have 5 set T1 or T2 and you summon your pet. Issue is that your set bonus is causing small amount of aggro because it applies resistances from the set bonus to the pet which is counted as a buff (I’d assume) and thus causing some small amount of aggro with it.
A side from that, there might be the same issue with the stamina from talents (need to test this one out) as that stamina increase is applied when your pet is summoned (you probably noticed that when summoning your pet which had full hp and suddenly it’s missing some hp when summoned).
Blizz can you look into this matter and fix how this aura and talents are applied on pet: e.g. check talents and gear bonuses and summon pet with those buffs applied already instead of applying it after summon