I don't know how they would have raids work with quests... when I was in a raid, I couldn't get quest items, kill things for quests, finish quests, or accept quests. I looked it up, and apparently you can't do anything with quests while in a raid.
You can however work on a quest when in a group, but a group has a max of 5, while a raid has a max of 40.
What they will probably do (I am assuming) is have some way of linking the objectives of raids together, making any required items something that always drops on a certain creature, or is always in a chest ect., and is soul bound and 1 only for inventory, making rewards what you get off the raid bosses/creatures. This way it would be similar to a quest without actualy being a quest, and you would be able to do it multiple times.
Warlocks can be very useful if you are planning on grouping somewhere and someone is a ways away, they can be summoned instead of taking however long to run to wherever the raid is. I think it mentions this somewhere in the article A1 posted... They can also provide extra tanks if the group is short on warriors.