Despite being an ICC boss, this is actually one of the easier bosses I have managed to solo. In fact I have wiped on the trash before this boss so many times that I eventually gave up and used an invisibility pot to get past them.
The reason this boss is easy is because when soloing, almost all the mechanics of this boss are circumvented. The boss only uses two abilities when soloing. First ability he uses is the slime puddle that spawns on the ground, covering an entire corner of the room. This has no impact whatsoever since the boss is tanked in the middle. The other ability the boss uses is the slime spray, which is channeled like Mind Flay, except it's..slime. This is a good thing since it does very little damage and hence provides time catch up on the healing as the boss melees very hard.
Aside from that the boss is simply a tank and spank. It does have an 8 min enrage timer which means at least 15.2k dps is required to beat it. This means that it is highly unlikely for priests to solo this on 10 man heroic mode due to the enrage timer even if they can outheal the damage output.