In-Game Parser.

[Krr]

You will have players just trying to maximize their numbers, even if it means playing their role incorrect because they want the output.

The only situation where you could possibly have this occur with DPS roles in a Second or Final Coil situation is a Bard refusing to sing. On top of this, all recent (T10+) content basically expects all players to be DPSing so hard that the only thing keeping them below their 100% uptime training dummy DPS is the boss occasionally turning invincible or moving out of range. Failing a mechanic causes you to die, dying causes your DPS to go down, so players looking to "max their DPS" will do whatever it takes to stay alive.

Outside of these fights that require near-perfect DPS peformance? There are no community gating tools that keep players from participating. Crystal Tower, story Trials, Dungeons, et al don't have scads of party finders saying "clear or kick", and they won't gain scads of players kicking people over their DPS all of a sudden. Even then, there's few situations where coping with a mechanic should meaningfully slow your DPS. You'll see a 10-20% decrease at worst, and that's usually due to super outdated stuff dying or triggering mechanics so fast nobody's job makes sense any more.

In fact, the only fight I can think of where "DPS focusing on maxing their numbers" would cause someone to 'fail' at a role is Moggle Mog EX. The rest of the time, ignoring a mechanic to burn is asking to die, which makes your DPS worse.