So guys, in any% do you think that Tutorial, Yeti, Stratus, Onyxia, Gol'Qayin, Rol'Qayin, Mol'Qayin and Avarice is the best route? Or there is a better one?
It's hard to say. You'd have to time how long moving between areas takes. Gut feeling tells me that tutorial>forest bosses>knight+mimic>volcano bosses, either with mask or with the slime, would be the fastest. But you could also go forest>knight+mimic>mask+truth, save warp back to start, kill stratus, save warp back again. Every boss except for the lava slime has a consistent(ish) quick-kill that you shouldn't die on, so it becomes a matter of movement efficiency rather than kill speed.