I've always stayed away from raids in other MMO's because they seem like work and I don't really want somebody yelling at me about how to kill a dragon, but when it is as simple as running up to a big rift in an area and hitting the join public group button, it makes it pretty accessible. You also are rewarded based on your contribution, so that works out good.
Admittedly, raiding in WoW takes a bit more organization as you need certain classes in the party but the "raiding" is the same, going to kill some big baddie.
How does it work in Rift? Say only dps and tanks happen to be in the raid, is it just a wipefest because no healers happened to wander by when a rift opened?