How would an optional, official parser be toxic?

[Legion88]

That's not my point. It can't be a gear check, because the issue people want gatekeeping fights for is not gear, but skill. And if they don't have the skill to beat it on launch, they need to practice till they can or they can't enter the instance. If they need to rely on better gear to beat the challenge, then it will be too late. You won't be able to be understanding, the gatekeeper will keep them out of the fight. The point is that with a gatekeeper like this, it will delay people from entering to prevent that. And by then, there won't be people who need newbies.

You misunderstand what a gatekeeper is.
The gatekeeper makes sure noone can go further without the required skill, because people without this skill wont be able to do anything beyond that point.
The gatekeeper checks if you are skilled enough with this job to have a chance by your own and don't need someone else to carry you.

A gatekeeper has to check your knowledge of the jobs rotation by a simple DPS check, has to check your general knowledge of game mechanics, like telgraphed AoEs, one hit by them and you're out and he has to check your general skill by mixing this up over a couple of phases.

If you can't pass this simple checks you are in no way able to to anything beyond then participate but never contribute.

And don't forget, the content behind the gatekeeper is even harder then the gatekeeper himself.