Very doable solo as a rogue.

I personally was a lvl 44 subtlety specced one and had no trouble. To do that you will need to get yourself into the corner as seen on the screenshot, sap the closest mob to you (ignore the boss and his posse, you are just right out of their line of sight) and proceed to loot the tablet. Keep your vanish off of cooldown just in case though.

All of the chain leading up to that is soloable as well.

Just did this on a level 49 druid, you wont aggro the boss or any mobs if you come out of stealth just right of the tablet and loot it.

Just solod this easily with my rogue at level 42 just stood with my back to the wall by the tablet looted then hearthed out. Hardest part was finding where the heck it was at!

Did this as a lvl 43 Druid; clearing the adds and trying to access the tablet without getting the boss' attention proved impossible - what worked was to jump up on the ledge (of the nearby pillar) in order to become totally out of LOS from the boss, as well as out of range of the adds i suspect. Getting up is easy enough if you move in behind the tablet and start bouncin'.

I just finished soloing Galgann as a level 42 Protection Paladin, a few tips about how to get there and kill Galgann:

I used the back entrance wich is described by the comments above, the first mob you have to kill is a 7k giant. He isn't very hard and only needs a bit of AoE to kill the adds he makes. When you have killed him, the hardest part before Galgann is next. There are two digger and one geomancer. I suggest to kill the miners first. I killed one miner and died, and when I respawned there were only 2 left, so that was cake, you only need to die. When you've killed them, you have kinda made it to Galgann, there are only bats patrolling. You only need to watch out for the scorpids, they have low health but do very fast, constant damage if you dont AoE them down quickly. When you've killed them you do some pretty easy trash where Galgann is.

Galgann:

Galgann has two geomancer (thankfully not miners, that'd be a nightmare). when you are ready, pick one of the geomancer and DPS them down A.S.A.P. This is very hard, and it could be good to be running around killing the adds, since Galgann does Fire Nova wich is.. bad, but you can decrase the damage it deals by moving far away from him. When the add is dead, DPS the other one and be running around to avoid the Nova. When he is dead, Galgann does not have much mana left, and just DPS him down, I needed one potion and a bubble. Note that he is immune to stun, so Fire Nova can't be interrupted

lvl 46 shammy

I died four times, but managed to get the tablet via the back door. I actually took the side of the room with the boss(I wasn't thinking, I guess). If you have some form of fire resistance, the boss isn't bad at this lvl and you end up w/a pretty blue to boot.

Took me about 20 min, but well worth the 9960xp (w/boa gear at lvl 46).

These are the same tablets that King Magni Bronzebeard of Ironforge used in the book ""The Shattering: Prelude to Cataclysm"" that turned him into diamond.

I felt so bad after finding that out, it's all my fault D: