If they're being a burden instead of helpful, and knowingly don't change, then let them know the entire party expects more.
If they refuse to improve, vote kick and replace with someone from the 98% of the game who likes playing in a helpful way.
If the vote kick doesn't work, you're wasting potential hours of your life on people being silly. Eat penalty, go craft or do beast dailies or something, try again.
All else fails and you've got time, try out your own "new playstyle", go full blown PLD healer or WHM tank or BLM melee.
Dumb people are everywhere. Don't try and fix them. Just smile and move on.