So, does that mean you would kick them?
For me it comes down to this. Are they trying? Can DPS hit aoe button? Can healer use something besides basic GCD single target heals? (like a cooldown) Can take pull wall to wall (at endgame dungeons, leveling is a different story) and then hold aggro? (don't even care if he stays in tank stance) If the tank is under geared for the endgame dungeon (why u do dis????) then that can be adjusted slightly.
If they can do these things than they are doing the basics and get a pass. There is alot of room past these points for people to be "leet". I do not see how any of this criteria would be picking on "casuals" because the vast majority of people I run random duty finder content with, are capable of at least that much.
How about we ask people to not be exceptionally rude, or exceptionally lazy. Gotta respect peoples time, we don't get enough of it in life to waste.