1. i do too. but there are certainly some that i prefer over others. and with 5.1 and 5.2, there's a lot more variety. not necessary to gear up, but they do help if you're not well connected: don't have a ton of gold to buy crafted gear, don't have friends who craft, aren't running with a newb friendly guild...
2. answered.
3. think of scenarios like a long elite group quest back in the day. reminds me of 'battle for undercity' quest thingy back in wrath or cata (don't remember), just minus the insane buffs. since you have a lock and a priest, you got great classes for scenarios cause you do need some kind of healing or else you'll have to stop to eat. my hunter's self heal is fine, my dk's self heal is fine and other guys love it when i bring my druid and shammy and can offheal them.
4. dungeons are more faceroll than ever. they are nowhere near the difficulty of cata dungeons. and once you're geared enough for LFR, you don't run dungeons anymore. o...'need' is the new 'greed'.
5. great new, unexplored continent. some absolutely awesome npc factions (that woulda made awesome player races). rares in each zone that are challenging and they drop some cool stuff. pet battles and farmville (i just like going to the farm cause the area is cool). new scope of buildings. its one of the more subtle things, but the scope of the buildings in MoP is a lot grander than before: villages have better scale, temples are impressive and the wall is massive.
6. don't have a lock or priest, but im like 99% sure that towards the end of MoP, they'll have LFR for old raids.