It isn't the only difference, although it is a very visible one, as rifts open up all over the place. But it really isn't about raiding, it's about ease of grouping. You run up to a rift and you are suddenly in a public group, working with people to shut it down. These type of automatic public groups are commonplace. They are really going after the idea of massively multiplayer in the MMO name. Grouping isn't just easy, it is automatic. These groups often turn into raid groups when they get big, but there is no management necessary like in an endgame raid.
The second big change is the class system. It allows for a ton of variety. I was upset that Blizzard never added new classes with the expansions (I thought the Death Knight was a bit of a cheat.) Rift allows me to really try some different types of characters, for example a cleric that can tank, DPS, or heal.
It's also just a completely different universe. The story and characters are refreshingly new for me, they've kept me engaged.
It's definitely a standard MMO, I just think it has elevated the genre by refining a lot of the mechanics other games have had. It's worth a try for anyone who enjoys MMO's.
Sounds interesting. Im not a huge lore guy and couldnt tell you anything about the WoW universe even after years of play. Just FYI, the bolded part is called a Paladin in WoW.