I don't play any of the classes you mentioned, but would like to give you some advice if you're looking for it.

If you're playing in the level 30 bracket. If you play the healer, run like hell around the map and try to survive the best you can. Most groups just zerg the healer because at level 30 it is quite easy to kill them and move on. If you're the dps, just go kill the healer with all of your team, with all 3 of you on him there's no way he can survive long, unless everyone's making mistakes.

Stay away from level 50 bracket unless you have ilvl 70 pvp gear or at least some of them. You will find very quickly that without it, you don't do much damage, or as a healer you tend to drop like a fly for the most part. I've seen some players survive quite well with some ilvl55 pvp and a mix of their pve 90, but if you're up against 4 ilvl 90 pvp, you're most likely not going to have a chance.

In the 50 bracket it's usually good to have your tank chase the healer and if there is a black mage, have your dps cover him. By this point many healers have learned and are good enough to survive well. Once the blackmage or even summoner dies, it's good to blitz the healer at once. If you know your team and feel good enough, nuke the healer at once and see if he goes down, if it becomes a chase, let the other 2 dps switch over to the ranged dps while the tank stays on the healer to avoid letting him free cast.

I didn't really get lot's of queues for the lv 40 bracket but same strategy as 50 would apply to kill the ranged dps sometimes then healer while tank was bothering healer. And if no ranged dps the straight for the healer. I've seen some nice plays by taking your tank and healer behind the wall opposite of where the enemy healer is. Have one dps chase the healer on that side, while the tank covers and testudo's the healer on the other side while killing the enmy tank and dps on your healer. That is if you play Pala, can make some unique strategies sometimes.

Other than stuff like this, no one can really teach you how to play, you have to go in and learn by yourself, even if it means wiping a lot. And don't let anyone get you down, for the most part people are really nice but you sometimes get yelled at for making a mistake or two Just learn from it, and keep grinding.