How would an optional, official parser be toxic?

[Bhearil]

To get good damage you need:

A: Learn the proper rotation and repeat it until it becomes muscle memory(if you need to think on any moment you didnt nail it yet)---> you can do this on a dummy for example
B: Learn the mechanics of the encounter to avoid losing dps due to gimmicks or even dieing--->Watch videos or just face the enemy as long as its needed

With those 2 perfectly clear (easier said than done, it takes time) you are already reaching a high level competence of your job and you should be fine on almost any content but the most demanding ones. Even then, there are more ways to further improve:

A: Learn what can you push with your ping and skill speed(like double weaving)
B: Customize your gear to get the best bang of your bucket stat pool
C: Coordinate with your team while using raid buffs

Just to mention a few.

None need a parser but to confirm what you should know already, only the most hardcore might get a small benefit by using a parser optimizating their jobs to the very limit but thats a tiny minority of the players and even on them, the gain is really minor