Depends what type of info if you're talking for pve, because the damage tallies in pvp are a lot less relevant especially considering that class pick, team composition, and whether or not you spend your time defending/frontlining vs actually pew-pewing to your heart's content will wildly affect this. Padding is also a thing, and you can perfectly have crazy high numbers but actually contribute so little to actual moves that matters or securing/assisting kills that it's far from telling the whole story. If anything, the pve habits (keep casting, keep things on cd etc) are generally the hint of poor pvp play, but good scoreboard padding.
On the other hand, pve is just about damage damage damage and even more damage. It has zero depth and no variables (beyond gear differences and limitations), so a pve DPS meter is absolutely not comparable.
It actually didn't, for the reasons I mentioned above. The reason people are toxic in pvp is like for any competitive online pvp game, they get mad at teamates for all the reasons in the world, be it teamates making genuine mistakes to just imagining that all their woes come from another teamate. Chat got toxic in Feast before the scoreboard appeared.