attunemen - easy even with one tank

moroes - in theory easy. But there your raid will get damaged by adds so you will need to care about healing whole raid. In the same time you gotta tank moroes and move warrior since moroes vanishes and you gotta catch him. And in the same time dpsing focusing dps. Pretty hard, also gotta make 1000 macros for all chars.

maiden - pretty easy tank, but how are you gonna dispel with 3 dispellers in the same time? afaik decursive doesnt work anymore in the way it did before 2.0

curator - there will be problem with outhealing sparkles' aoe I suppose, otherwise it is easy.

illhoof - you gotta have 2 tanks here for imp and the boss himself. You gotta have good gear on MT so he can survive it. Also you gotta heal all the time AoE people, chained person, 2 tanks. Easy? no

shade of aran - elementals will be hard, you can ofc focus them but they are doing insane damage on single target, you gotta care about making them nuking one target you want them to nuke, thats pretty hard. In the same time you will be nuked by aran himself.

netherspite - switching between 6 characters all the time is confusing... also you have to do good control on tanks and aoe heals. In theory easy, on practice I'd say it is nearly impossible.

Nightbane - dont forget you will need to move chars from charred earth, also they can be feared under nb which might cause insta death, also you will need to reposition them after fear

Prince - you have to move your raid all the time from infernals, same shit with warrior. Flying axes are bastards too with help of shadow volley

So it is very very hard and some fights are nearly impossible because you have to do constantly healing (and conserve mana) on a few targets or whole raid and in the same time tank/dps/do other bossfight stuff...