Actually, some classes do get a boost somewhere in that region. Like BM hunters for example - a lot of their damage lies in artifact abilities. Hati Beast cleave and Kill command alone account to 5-20% of the damage (depending on single or multitarget). 15% from final traits, 10-30% on all basic rotational abilities, final golden trait is easily 10%+ damage. All of that is cumulative. I would say that the boost at the very least is bordering 60% line mentioned by TS. Likely significantly more than that.