SE's most difinitive statement yet on parsers

[Gormogon]

I still would like to know how using a parser helps someone "gain an advantage". Are you admitting that otherwise, people would be using bad rotations

That's a misconception.

It's not that it's an advantage in making you a better player. It's an advantage in spotting how bad a bad player is under performing and it helps justify getting rid of them from the group. Something you can do without a parser by just looking at ilvl and comparing it to someone good you occasionally play with. Though without parsers players will tend to just whatever the situation but with parser information it just gets nasty.

Since that's where parsers get used more seriously more often which is in groups in dungeons/raids.

A bad player is gonna be bad regardless of having a parsers. (Dare you to tell me a 3 year old will get better with parsers)
A good player is gonna be good regardless of having a parser.

Top excelling players don't need parsers to judge timings, stats, etc. It's their way of life to constantly do this especially when changes are introduced.