My friend solo'd it yesterday with a Barb and it he said it was easier than he expected. He said that he used Cleave/Rupture for dealing with the little dorks. I know it's probably not much help for you, just throwing it out there. Not sure how your Wizard friend will fare.
The shadows don't do much damage. The main threat is they come in huge swarms and can trap you on a Desecrate. Not so much a problem since you can leap or charge and he can teleport.
Earthquake is really good here, but he does randomly leave the arena so try and time it well.
I'd leave as little to chance as possible and just wrath quake him as soon as he appears. Terror Demons (like Iskatu) do a ton of damage and all offensive affixes (like Desecrator) are based on enemy damage. He has very low HP though... would be about 2 mil in a 2 player game on Inferno.