I have a lot of this stuff more or less memorized, actually; I started being interested in this when the devs wrote a blog post about the Vicious token and its fine-tunings (don't have the link handy, but you can find one on these forums if you search a bit). Off the top of my head (along with a couple of checks to my videos), the standard boss damage of 75 is modified according to the following "tiers":
Hard tier 1: 82 (x1.1)
Hard tier 2: 97 (x1.3)
Vicious (natural): 105 (x1.4)
Vicious (token): 120 (x1.6)
I *think* that the bosses' HP is modified accordingly, except for the Vicious Token modifier which is actually x2 for HP instead of 1.6.
The dungeons are distributed into the tiers as follows (? signals I'm not sure, with the provision that even the ones that don't have ? could be wrong; heck, I might be missing a tier in there)
Normal: All "normal" dungeons, Hexx Ruins, Berserker's Camp
Hard tier 1: Doubledoom, Havendale Bridge, Creeplight Ruins (?), Rock Garden, Cursed Oasis (?)
Hard tier 2: Labyrinth, Ick Swamp, Halls of Steel (Hard), Shifting Passages, Magma Mines, Slime Pits
Vicious (natural): All "vicious" dificulty dungeons (except VGT; see below), Grimm's Grotto (!)
Note1: As mentioned in the posts above, Aequitas in the Northern Desert is actually a completely different boss than regular Aequitas. I don't know if it's regular Aequitas stats lowered significantly or just plain different ones.
Note2: When doing the "bankers" quests at the very beginning of the game, the overall monster stats are lowered. Possibly to the level of Hobbler's Hold? Not sure.
Note3: Hard Gaan-Telet and Vicious Gaan-Telet, if I'm not mistaken, use the same regular monster stats for the ground floor and first three floors. I believe this is the "Hard tier 2" (x1.3) modifier. The difference, of course is that VGT's floors keep modifying the monster stats further per floor. I don't feel I need to mention Horatio here
EDIT: Note4: I've never tried it out myself (and I can't check since I don't have access to the game right now), but from what I remember reading on these forums, the stats of the bosses native to the vicious dungeons (Namtar, The Avatar, etc.) are considered "base" and are therefore fully modified by the Vicious Token's x1.6 modifier. This would be in contrast to, for instance, Dragon Isles' version of The Firstborn, which is already at x1.4 in the regular version of Dragon Isles and therefore is only boosted "slightly" (ahaha) in comparison. THESE ARE MERELY MY ASSUMPTIONS!
Since dislekcia mentions that progression affects the modifiers, I should mention that pretty much all of this is based on a fully unlocked kingdom. If anyone has corrections (or knows that I'm flat out wrong), I'd love to hear it!