You can have the highest number of kills in CC or FL and still lose the match because you ignored the objectives or traded kills.
Similarly you can heal like a boss and put up great damage but get no kills, but you stuck with your team and got a high number of assists and a low number of deaths. maybe your team won, maybe they lost, depending upon cc or FL, but you can look at their deaths to see how they did.

I don't see why there wouldn't be a personal log that would be displayed in PVE, for % active, deaths, skills, overhealing, and damage.

By the way, the discussion about which is more toxic is moot, yes there can be toxicity in PVP, however that also exists in PVE. It is perfectly possible to be competitive in PVP without being "toxic" just as there are many extremely skilled PVErs that are not in the least toxic.