The only thing leaving BST behind other jobs in terms of usefulness to a party is party buffs. You can't really balance BST against them with new pets, gear, or abilities because those things will change depending on the party make up.

Let's say you tried to improve BST with a stronger DD pet. You could either make a pet that's strong when in an unbuffed party, but falls behind when in a party with buffs. That's what we have now. Or you could make a pet that keep sup with fully buffed WAR's or other strong DD's, that then is way too powerful when you're solo or in an unbuffed group.

Same with new gear. Every piece of pet damage enhancing gear requires me to weaken the master for the sake of the pet. I only end up using them in the rare instance where only the pet is fighting.

And since you've already shot down letting party buffs hit pets like they do companion NPC's....

My solution is to simply remove Beast Healer or Killer Instinct merits and replace it with Empathy. Or perhaps make it one of those level 99 Tier 3 merit categories you hinted at earlier. Just a straight copy of DRG's trait. Might need to make it work on Reward, or ready, or a Stay followed by a Heel, but working the same way; level 1 transfers 1 buff to the pet upon reward, level 5 transfers 5 buffs to the pet upon reward.

It fixes everything.