As ret, naxx 10 is simple and ToC 10 is also simple (but more damage, I had to pop LoH once or twice). Haven't tried Ulduar or ICC yet. It's naxx 25 I can't handle - specifically, Gluth.
Yeah, Gluth is still a pain. The only way I've been able to down him in 25-man is with a hunter helping me out. She kites the adds, and her pet taunts off of me so my Mortal Wound stacks drop off.
I imagine if you prepot and blow your cooldowns (assuming you're using either HA or SW) at once, you might be able to down him despite the healing he gets from the zombies, but I doubt it unless you're pretty well geared.
Anyway, more to the point of the thread, Naxx 10 is pretty easily soloed without the need to worry about picking specific talents, with the only exceptions possibly being Patchwerk and Gluth. Naxx 25 is a bit more of a challenge; like I said, I needed a hunter to give me a hand with Gluth, and I barely managed to beat Patchwerk's enrage as Prot.
I haven't tried to solo ToC, but I've done a fair bit of Ulduar on my own. Flame Leviathan is a cinch once you've destroyed the towers - simply stay as far back as possible, and when the fight starts, pelt him with pyrium. Iron Council is fairly simple as Prot, though you might end up getting killed by that debuff, usually once they're already dead.
Mimiron was the only boss I had a lot of trouble with due to our less than stellar ranged ability, but what worked for me was blowing AW and spamming the ever living crap out of HoW until the head was almost
dead, then killing the base and torso with AoE before quickly finishing the head off.
XT was a little irritating, but I find that the easiest way to deal with him is to go with Clemency as your T4 talent so you get more use out of HoP. There's usually more than a minute between Tantrums, so Forbearance isn't an issue really, and I don't see the fight lasting fifteen minutes. (Two HoP CDs and DS.) You can also glyph DP; it won't outright negate the damage of Tantrum, but it'll make it a lot easier to heal through.