The easy way to defeat Twin Emperors: Vek’lor & Vek’nilash is to nuke the boss that takes physical damage. You can nuke him with Kill Command, A murder of crows and with the damage done by your pet.
At level 90, your damage will be higher than their healing. Ignore the boss that takes only magical damage. Ignore the old strategy when you need to split them.
Temple of Ahn’Qiraj (AQ40) is very easy to be soloed, except the boss mentioned above. Now that you know about this boss encounter, it should be a piece of cake.
C’thun
C’Thun is very easy. Nuke the boss at start. Once you destroy the first tentacle, approach the black cloud that is around the boss. You will be teleported to a new location. Destroy the two tentacles from there and move your character in the circle between the two tentacles.
You will be teleported back and now you can finish C’Thun.
Viscidus is another tricky boss. You can drop his health until “1” but he won’t die. To defeat him, you need frost damage. Chimeras have an ability that has frost damage. Tame one and bring it for this fight if you want to kill this boss.
Rewards. There are almost no cool hunter items for transmogrification. You can get reputation with Brood of Nozdormu, a vanilla faction and some new companion pets that can reward you with some gold if you plan to sell them into the auction house.