I think Jake is probably okay, that Nergal level speed means he's eating doubles constantly. Puny Mages can deal with them if they don't also have puny durability... which I suppose is also a thing.
Hetzel is a tad weird. I would see him as able to get wins vs. PCs because hey if you can't break his regen, you don't win, but I know a lot of other people disagree and don't tiebreak for bosses in such cases, and then Jogurt defeats Hetzel on basis of a damage-done tiebreak. (Okay, I guess there are certain PCs with insanely horrid PDef AND only short-range attacks whom he might do damage to... but that is uber-rare.) So basically I think he's fine, but for others he can't win. EDIT: From chatting with others... equal-XP Vika might take 1 damage or something. DL equal-XP Vika has 18.5 Def endgame, but Vika needs those levels from E-2 & E-3, so she theoretically might still have 16 Def in E-1, and thus take 1 damage from Hetzel's 17 Str + 0 power staff counter. Everyone else either can't initiate (Herons, unshifted laguz) or tink or both tink & can attack from range 2 anyway. You need defense so bad you take 150% normal damage or worse, I think.)