Why are low standards for dps acceptable?

[Kaurie]

Or they are still in the process of trying to understand it? Maybe because there is no rule saying they can't join level 60 content without a complete understanding of their skills? Maybe they gave up trying to understand and needed help and that level 60 dungeon happened to be the first place someone did help them. Just because they don't understand something fully yet means they shouldn't be able to take part in content they have paid for?

There is no rule, there is just etiquette and being courteous. You're actions affect 3 other people in a duty, so it's appreciated if you understand how to contribute effectively.

Generally speaking, etiquette is never hard-ruled.