This is the end.

[Kosmos992k]

Says the person that feels they can play how they want regardless of how it affects the party.

And yet, Ironically, you are not only doing the same thing, but you are also reinforcing the kind of nonsense that happens in dungeons as described by the OP.

Who are you to decide or judge whether another player is doing things the best way, or playing to their max. Even if they aren't who are you to tell them so? Is it your role to sit in judgement of others? Honestly, unless it's end-game or a raid, what does it matter? Offer constructive advice in a positive manner if you must. But critiquing someone's play is just asking for trouble.

I wish more people could realize that it's not their place to judge, and they are not the be all and end all of what constitutes a high playing standard.