Drake chomp attack
I can guarantee you it does use this attack as ive seen it happen. But when it happens I can’t say. If theres a difference between it and its normal attack animation its very small becuase I havnt noticed it. Its possible it only uses it when its taken significant damage like you said. Ive seen it used mostly in TPvP by seeing seemingly random high number crits coming from the drake when it wasnt using tail swipe.
All of that together makes isolating it a PITA.
Long ago when the game was first released, the skill was bugged and actually healed the enemy target instead of your pet.
https://forum-en.gw2archive.eu/forum/professions/ranger/Drake-Chomp-requesting-testing/first
Fixed in a patch a couple months later.
https://forum-en.gw2archive.eu/forum/info/updates/Game-Update-Notes-March-26-2013/first#post1856151
The build editor says “bite a foe and gain health” with a damage of 1422.
I see a lot of bite attacks for about the expected 500-ish damage
1422-500 = 922, which is suspiciously close to the amount the drake is supposed to heal itself by with the attack (965).
You may want to run some tests to see if that old bug hasn’t resurfaced.
Managed to catch it on video. Chomp did about 1300 and healed about 680
The drake used it when it was pretty far down on health (maybe 60%)
I think all pets use their heal skill in that range (65% ish). That can be handy for knowing when moas are going to AoE heal. A looong time ago I used moas and knew the pattern, I think it was when any ally or the moa itself was under about 65, 70% health and in range.