To start off, I know how hard it is to find Tank and Heals for Raids, and even now for Daily Heroics. It's a pain for the DPSers, sitting there for 15min waiting for a group, cuz even with a cross realm gig for the randoms, seems like there is still a short supply of healers and tanks. I've heard numerous people complain about not wanting to heal/tank. And that is their right. They pay $15 a month for this game, they should play how they want and what they enjoy playing as. That said...
As I said, I know it sucks being in a group and all your needing is that healer or tank. If you are putting together a group, whether it be a raid or daily random, you get 1 time to ask everyone in the group(people capable of these roles of course) if they want to tank/heal. That is your 1 shot. As it's always been in GoP, no one likes beggers. Don't sit there and beg so-and-so to heal, or make lil comments about how "It would be easier if so-and-so tanked...". It's just annoying, and putting guilt trips on those people doesn't help their attitude.
NO ONE should feel obligated or pushed into a role they don't want to play. That is unfair to the player.
I hope you all take this under consideration, especially you players that have had these instances happen to you.