Been solo farming Karazhan, Gruul's Lair, Magtheridon and Malygos for T4 gear and lookalike weapon to Transmogrify. My spec is Elemental since my main spec, and thus gear, is for Restoration. The spec I used is as follows, including glyphs: Talent Calculator - World of Warcraft
The spec is primarily tailored for Malygos, which can be the hardest one of these, depending on how bad RNG High King has. Karazhan is a total pushover now. No boss should pose any significant threat, although I skipped half of them since I only need gear from Moroes, Curator and Prince, so I don't know if some bosses have hard mechanics.Basic strategies
These apply to all bosses. Primary "rotation" outside exceptions is Flame Shock debuff > Earth Shock > Lava Burst > Lightning Bolt. Earth Shock is used as a filler shock mainly to gain 20% attack speed reduction whenever it's off cooldown and Flame Shock doesn't need to be cast, as it reduces the damage output especially on Malygos by a lot. Main heal you'll want to use is Greater Healing Wave. Try to time your heals in a way that you'll have both Clearcasting and Focused Insights. Use Flametongue Weapon enchant. As for totems, Healing Stream and Wrath of Air are no brainier, fire totem is either Fire Elemental (usually needed at specific times, especially on High King), else Searing Totem. Just make sure you have one down all the time to get Totemic Wrath spellpower bonus. Earth Totem is usually Stoneclaw, but sometimes Earth Elemental is the key to the fight and Tremor is useful if the boss has fear effects. It's not worth it to pop Stoneskin between Stoneclaws. Use Thunderstorm on every cooldown once you're down to 90% or less mana. This is to ensure you'll have enough mana to carry on through the fight. Use Stoneclaw Totem on every cooldown if you don't have a specific moment when you need it and if your Earth Elemental is not out. Always use Lightning Shield, Water Shield is not worth it with Rolling Thunder talent, recent Water Shield nerfs and need to continuously recast it.High King Maulgar
The epitome of RNG, as far as soloing goes. First time I was here, I spent 9 hours trying to figure out the boss, it's that hard. The strategy is to pop Fire Elemental, Heroism and Elemental Mastery right at the start and nuke down Blindeye. Try to interrupt him if you want, but I didn't notice much difference whether I tried or not. Half the time he has shield on anyways so that interrupt doesn't work anyways. Once he's dead, your Fire Elemental is probably dead or close to that. Pop Earth Elemental and proceed on Olm. You should still have hefty amount of Heroism left, so try to bring Olm down while still on it. If he decides to, he can chain Death Coil you and you'll die for sure. Once you manage to kill him, hopefully your Earth Elemental is still alive. If he is, try to cast a few heals on it, then kill Kiggler. Once again, if you get chain Polymorhped, your elemental will die if it's not already dead and you will soon afterwards. If you manage to kill Kiggler, the fight is pretty easy, at least not much RNG elements are involved. Start to bring down Maulgar while making sure you're at high health, after 50% Maulgar likes to use Fear. It can be broken with Tremor Totem, but sometimes he just casts it more often than you can Tremor. After Maulgar dies, you'll still have to kill Krosh, just purge his shield and kill him.Gruul the Dragonkiller
Just a tank and spank, really easy. If you've done High King, this one is like a walk in the park.Magtheridon
The boss itself is pretty easy, and the adds are too if you know what to do. To start the fight, select one of the adds, pop Heroism and burn it down. Drop down Earth Elemental and let him pick up the rest of the adds. Then jog to max distance, pick one of the Channelers and start nuking. He'll come to you and be out of the range to be healed by the other Channelers that are focusing the Earth Elemental. Rinse and repeat until all the Channelers are dead. Interrupting them should not be necessary if you have Heroism, but after it wears off, you might want to do it, depending on how much burst you can apply to them. Magtheridon himself is easy, stay out of rock showers, no need to click any cubes, just burn him down while maintaining your health.Malygos 10man
He's hard, but fun as well, and not just tedious like High King. First phase is what the fight is all about, maintaining your mana while keeping yourself alive, killing the sparks and DPSing the boss in the meanwhile. Some luck with Spark positions are helpful but ultimately not needed. It's not that important to save Heroism for the first phase transition since phase 3 is really easy and there's no massive benefit from getting the boss to as low health as possible before phase 3. So just use heroism when you get bad luck with healing crits or generally when needed, else save it for phase 2. Also if you happen to get 2 sparks in one place, Heroism can be great so you can enter phase 2 with more mana.
Start the fight and use the rotation discussed in basic strategies. Killing the Sparks can be challenging, especially if you're on relatively low health. Always DPS the boss from the buff that sparks leave behind. When maintaining your health, remember that Breath takes around 25% of your healthpool and you won't be able to heal in his Storm ability. Try to avoid having to spam heals in general and always aim to have Focused Insights and Clearcasting up when casting a heal. After all, mana is what makes or breaks the phase 1.
After phase 2 starts, kill the two Nexus Lords as fast as possible. If you still have Heroism, this is the best time to use it. Once they are dead, get on a disc and kill the rest of the adds, one by one. Stay up in the air during Deep Breath and don't forget to go pretty low altitude when killing the last add, since you'll be dismounted and fall to the platform.
Phase 3 is really easy, as long as you know what you're doing, and if you've been here in WotLK, you probably do. Whatever you do, don't let the stack fall off from the boss. Always use 5 combo point stacks since you'll have to heal yourself inbetween too. When he focuses a beam on you, use 1 combo point shield on it, but not in expense of dropping your stack. If you're low on health, throw the hot on yourself but remember that once you cast a hot, your combo points on the boss are gone if you had any. When the boss casts lightning cloud thngy, simply move away from it. And one more thing, never let the stack fall off from the boss. That's it really.