Mimiron isn't too bad until Phase 4.
Phase 1) mini FL just pew pew, avoid bad stuff, when he uses plasma cannon (the big channeled move that hurts) pop ams or some other sort of CD and heal through it. Don't hit mines if you can, avoid shock blast.
Phase 2) When he does his wind up, stay behind him. When he fires a missile at you, move away from the impact point. It will kill you, does over 2 million damage last time I got hit by it.
Phase3) kill adds that spawn, use the magnetic thing from the large adds to bring the head down to dps. Pew pew, it'll go down fairly quickly and then the fun begins.
Phase 4) This is a good test of your awareness of what's going on. You need to kill all four parts within a fairly short window of eachother. The problem is only ranged attacks, Death and Decay, pestilence done off the middle part, and Heart Strike off the middle part will hit the head. I reccomend having a macro to fire off Death Coils at the head to try and take them down equally. If the part repairs itself, it comes back at full health. Sucks for the bottom two parts, really sucks for the head. This is also very healing intense while being something of a dps check. This will probably take a few attempts to get, but the feeling of killing mimiron is second only to Yogg-saron.
General Vezaxx is relatively simple. Keep in mind, to prevent hard mode just kill one of the saronite vapors and then just kill the boss. A couple things to note with this fight (since its pretty much a tank and spank with a 20% melee attack speed reduction).
1) Interrupt searing flames or use AMS for it. It reduces your armor and makes stuff actually hurt. Especially when he becomes empowered, you'll have to use IBF or some sort of cooldown otherwise you're in danger of being overpowered.
2) The shadow crashes that are very avoidable at a range, are next to impossible to avoid as melee and do a decent knockback. Let them knock you across the room somewhere, do not put yourself against a wall. Reasoning is they also reduce healing and you're not taking a large amount of damage, but just enough to break blood shields. This eventually makes it to where he can become a threat if you just stand in it. Searing flames gets off and you'll be in real trouble when he starts to hit you.
Yogg-Saron, the big bad boss of Ulduar and tied for my favorite solo that I've done so far (Lich King just had an awesome feel to it even if its more of a gear thing). With four keepers up it isn't too bad, your dps will be strong, you run around fairly quickly, you can regain sanity if the rng gods feel like smiting you, Hodir can save you if you get into a jam, and Thorim kills the adds in the final phase.
Phase 1) I usually just run through several clouds to try and get it done quickly. You don't want to pull too many because extra ones after the phase is over will have to be killed and I like using the transition as time to let runes regenerate. Be aware of the healing debuff, and the debuffs that sara puts on you.
Phase 2) Starts after getting enough adds to explode on sara and she begins a monologue. Clean up any adds get and out of the center area. Right at the end of the monologue drop a Death and Decay on yourself because you're going to get grabbed by a constrictor tentacle. You'll have 2 -3 of these happen to you, so be ready for it. Blood boil to help it die faster. You now have crushers and corrupting tentacles to deal with. RNG may put them closer or farther apart from eachother. This is what makes this portion of the fight so difficult. The corruptors do a few debuffs to you.
1) Leaching Poison: Ticking dot for nature damage, negligible
2) Curse of doom: Deals shadow damage after a time, negligible
3) Apathy: causes a big slow in movement speed, annoying when tentacles are far apart and/or you're just going into a brain portal
4) Black Plague: Causes random stuns to occur during a 30 second period, very annoying but you can use IBF to get a 12 second period of not getting stunned if you're trying to get somewhere in a hurry/kill something off.
All of these can be interrupted during their casts or amsed to avoid them. Mimiron also slows all but the first cast on them. I reccomend trying to ams Apathy or Black Plauge. If you have a Purification Potion then you can use it to drop Black Plague when you go into the brain room but Apathy will not be removed.
Crusher tentacles just need to be tanked and killed, if they're left alone they begin channeling a debuff which reduces your attack power. Depending on your gear this may prevent you from doing the brain room in one phase (which is your goal, after that things get really iffy on if you'll survive to another brain room).