Since STS is looking at tweaking the passive for Arcane pets, why not consider adding a unique passive aura for each arcane pet instead of just adjusting the normal parameters (% reduce armour, % reduce hit, % reduce crit, etc)? We can even have nice particles to make them really look really cool.

Just some ideas,

Hammerjaw: Thorns aura (reflect % damage)
Glacian: Freeze aura (slows attack/movement speed)
Samael: Regeneration aura (regen life/mana, which is already in place)
Brothers Whim: Defence aura (increase armor)
Singe: Might aura (increase damage/attack speed)