He is soloable via kiting as a shadow priest like the common elites in that area are, except it's harder as he cannot be feared.  Make sure you have a clear running line, and equip a +run speed item.  After that, keep all your debuffs and DOTs on him, nuke when you have the space, and remember that his knockback often gives you the space to throw a Mind Blast in.  You have to hit him with something every few seconds as you run to keep him from resetting (SW:D and VE will do). Kiting also prevents the shards from aggroing you.  If they do spawn at inopportune times and aggro you, they're easily outrun, anyway.