Day 2 (post-wipe) at my garrison menagerie:
Tirs and
Fiero (all legendary)
No team-wide buff. Just hard hitting pets.
Compared to the previous menagerie battles, I found this one to be a decent challenge. Both pets hit hard and use their attacks well.
I'm not confident that my team was the best against them, but it worked the multiple times I faced them. My team consisted of: [pet]Swamp Croaker[/pet] (B/B but I think H/B might be better, 1,1,2), [pet]Spawn of G'nathus[/pet] (1,1,1), and [pet]Emperor Crab[/pet] (H/H 2,1,1). Breeds are just what I had in my Pet Journal, so don't take what I used too seriously.
My main goal against Tirs and Fiero was avoid/survive their large hits ([ability]Pump[/ability] and [ability]Cataclysm[/ability]), and use strong attacks against them (both are elemental).
The fight against Tirs goes pretty much as expected. He uses [ability]Acid Rain[/ability], [ability]Pump[/ability], Pump, and then alternates between those two abilities and [ability]Renewing Mists[/ability] (but he doesn't recast mists if its still active on him, smart). My Swamp Croaker can squeak by this first encounter with just a smidgen of health left for the next pet.
From there, though, I'm not 100% sure which pet would be best to bring in. Spawn of G'nathus or Emperor Crab? I played around with using both as the second pet, but settled with the crab the majority of the time. G'nathus' [ability]Swallow You Whole[/ability] ability came in handy towards the end of the fight (if my crab died, which it did the majority of the time but it depended on whether or not Cataclysm hit).
I hope someone else can come up with a better team for this fight. I'm able to defeat them using what I've listed, but only just. It would be nice to have a more robust team for a more confident win.