Not my thing, I’ve done him because he’s easy if you stay in the spot and know how to use a grog (especially with Maya), but ehhh… Sal’s the only character I’ve fought him “legitimately” with, putting my back to the wall and grog harolding him like a MF’er while teammates hid behind the rock… I do like the Pitchfork and thank yout to some random person who dropped a Grounded Hide of Terra in my game once so I could play melee Zero, but I’m not a fan to be honest of that fight…
I’ve never gotten anything too remarkable from the Terra chests, I think the best was an e-tech corrosive Vladov blaster… but RNG is RNG.
I’ve gotten a few legendaries out of the red chest in the Bunker but I don’t think it’s anything special… I’ve just farmed the bunker… a LOT. Bound to get something eventually. 
Ive had decent luck with the wattle gobbler chests. mainly i find useful purples but I have found my only 2 Butchers in those chests.
Official name? No
Are they special in anyway? No
Do they have better drop rates? No
What do I have to say? Nothing, if you farm enough you’ll see good stuff eventually.
actually the one in the “VAULT OF THE WARRIOR” is a little different as there is a BAR Challenge connected to finding it, but other then that there is nothing else special about it
I don’t think any of these chests are particularly different from each other. I’ve got more legendaries out of the red Dahl chests than any other but that should just be RNG doing it’s work.
As for hard to reach chests I think I remember there being one on top of the broken road in Hunter’s Grotto. You need to enter from Ardorton and you can’t reach it in any other way than rocket jumping I think.