"Wave 2: Damage shortage is 100% a result of defeating enemies before the additional damage was fired (to be fair, the damage still fired, it just didn't have any targets left).
Damage numbers in wave 5 line up with the PvE difficulty override for each unit if you assume that 2 additional hits were dealt to each unit (looks like most were non-crits). So it looks like the on-screen numbers were not all displayed due to lag (similar to how certain animations don't fully display when graphic intensity increases) The damage was still dealt, however."