A couple other thoughts/ideas on pet buffs. Since big pet damage is based on crits, why not make some procs work off crits? Doesn't have to work on all pets, but this could provide some different ways for procs to occur, instead of when equipped/based off delay/based off being used. These ideas also give BMs a couple ways to help against DoTs, since that is probably their biggest weakness.
Some examples:
Stalker - when this pet crits, the vamp heal doubles as a cure, and cures pending DoTs. This would just be the part of the heal that comes from stalkers, not Conq quiver/rune/etc, so 8% with 1, 16% with 2 to start, would double as a cure.
Devourer - when this pet crits, the wound damage is applied to all opponents as a 10 second bleed.
Companion - When this pet crits, X% of the crit is applied as an AoE absorption shield to your team ( think like Iron Shell gem, X = mitigation on pet)
Tommy - When this pet crits, the next heal gem used gains an additional XX% strength. XX = Heal proc on pet. (As stated, pet is already strongest/most used, so buff should be something odd..this would give healers a different choice...plus 1 gem per tier)
Cuddlebug - When this pet crits, the next detrimental gem used against you will be prevented. (For uptier, can add 1 gem/level) This one *might* be a little op once uptiered, but currently no one active has over a tier 3 pet that I have seen, but that will be the joy of uptiering them
Lizard - When this pet crits, the poison applied is doubled, and adds an equivalent HoT on your friendly target.
Badger - When this pet crits, your next melee attack will be a crit. (For uptier, it could add 1 attack per tier...unlimited stacking, but only counts 1 hit out of DA/Quads/Etc)
Flesheater - When this pet crits, it's next attack avoids AC as well as mitigation.
Timmy - When this pet crits, your character giggles...or maybe groans. Not sure which would be better.