I know, that bonus power increases damage and theoretically it also increases stagger, but does it increase cleave? And if yes, then I have a more specific question - can power vs increase cleave? Because from my tests on modded realm it can not.
IIrc bonus power does increase cleave, power vs does not.
Hero Power indeed does affect cleave, or at least it should. It is a lot more dependent on a weapon’s base cleave than Power, though, so I don’t think Power vs. whatever is usually enough to affect it, at least noticeably. Once something cleaves five targets (where 20% would be effective, allowing one additional target), it gets quite hard to notice changes on it.
Granted, I don’t know exactly how fractional cleave and Power adds work, but considering Cleave amounts and percentages, it’s very unlikely to make a significant impact.