1. Easiest of any major MMO I have played. I began playing MMOs back in AC/early EQ up to WOW and it's descendants.
2. Tier 1 raid content is PUG'd commonly on most of the servers I have played on; 7 total. Due to the sparsity of the raid content progression in Rift happens rapidly.
3. There is a wardrobe system similar to Everquest 2 or Lord of the Rings Online. One can be decked out in relics but appear as a level 1 character if they so choose.
4. No. Rift's raids are very casual friendly. With 10man raids having separate zones & lockouts but awarding lateral gear to 20 man raids. 10 mans are literal, 40min-1hour affairs for all but the most incompetent. Often PUG'd. Also raid passable crafted items, open world currency bought items and very short upgrade cycle for tier 1 raid items are offered.
20 man raids are shorter and less involved than WOW or EQ raids. There are no "hard mode" versions. Just one raid a week for about 1 or 2 hours. Most causal raid guilds I have browsed raid 3 hours a week.
The bottom line is Rift raiding is very fun, but shorter and there is simply less of it than in other games.
I would fully expect Rift raiding to follow the World of Warcraft model as it matures. That is the intention of Rift; it's not an MMO for people who wish to escape WOW, so to speak. It was intended to be an MMO for people that wanted a newer version of World of Warcraft.
Or as one guild mate put it; Rift is not WOW 2.0, it's WOW 2k11.
I enjoy that a lot, personally.
One last tidbit; in Rift there are few iconic armor sets or even armor meant to be distinctive- a warrior can wear plate but appear as in full mage gear, for example. The armor sets often borrow the models of common gear as well. So coupled with the wardrobe system, one can craft an appearance unique to them without necessarily wearing Wrathful Vengeance of the Ice Crown Raider gear or somesuch.
I have one and only one question for you! Have you been in Hammerknell Fortress?