The other option is ignorance. Also not sure if kicking people who can't meet dps checks is all that "horrid." Sure, it'd be better if people helped out, but by the time people are capped and doing endgame, there's a reasonable expectation for people to attempt to learn their role. If they can't do what they signed up to do, then helping them or kicking them are both viable options, one's just more polite. And it goes back to the double-standard of the other roles; if a healer isn't able to meet a heal check it's immediately obvious. Why is it okay for dps to get a pass if they wipe the group? If you have 3 dps at 800+ and one dps at 400 and fail a dps check, it's blamed on all 4 dps. That's not cool.
The post was pretty long to quote the whole thing, so I parsed for a thesis statement (heheh). Sorry to misrepresent you, though, it's true that I kinda did.