An alternative to parsers...

[Erys]

Better idea:

Stop caring about your DPS. There are training dummies, use those.
The reason people keep asking for legit parsers is so they can do that kind of "low dps=kick" nonsense. No parser, no legit reason to kick. People using unauthorized tools = "report for cheating", people in this game are actually rather shameless and you can figure out who is using them just by looking at the website they upload the parses to.

First off, you don't equate training dummies to fights. Dps fluctuates depending on uptime, party buffs and cooldown optimization which vary on a fight by fight basis.

Second, you don't need a parser to tell who is underperforming. "But but but if you are looking at others you are most likely underperforming", sorry but no. Any player worth their salt can perform their rotations by muscle memory and only need to pay attention to mechanics. Also during openers, arguably the moment of truth to tell if your average player knows what they are doing, the bosses funny enough don't have any mechanics so you can scrutinize everyone.
Another good way to tell performance is rotational cycles, if you know how many rotations a good party go through you can figure out something is amiss. And depending on the difference between good and your df roll you can almost pinpoint who is underperforming.

And by no means I'm encouraging anyone to kick people everywhere. I'd rather teach people than just kick them right off the bat, but if their response is overly negative they are getting the boot and a nice spot in a blacklist.

PS: I forgot you make a third point of every people in that website using said tools. But you know your name can be there and not being able to parse at all, right? I mean, I play on ps4 exclusively and my name is in there. How am I using said tools exactly?