The Ogre Boss is soloable, but only, if you got the right class, a merc and good gear. For example my lvl 50 berserker can solo the boss. A strong highlvl crusader can do it aswell (even easier i believe, because he doesn't get to low hp like a zerker). I even did it with my hunter.
Anyway, the point is you can only solo that boss when you are at a much higher level (~45) and you need good gear for that (gear from Hill Giant, Gazrow, Broodmother and Garg). If your lvl/gear is lower/weaker than that, I think it's almost impossible.
The tactic about the boss is: The shaman turns himself invulnerable and starts channeling a spell. That is when you can kill the 4 lanterns. Each lantern kill will drain you 15 mana. The lanterns provide the shaman with mana and if he reaches 500/500 he will unleash lightning on every enemy. The lightning is too strong for any group, so you have to kill the lanterns before the shaman gets to max mana. So just kill the lanterns and attack the warrior boss until he reaches ~3k hp. That is the point when the shaman turns the warrior invulnerable and the shaman himself is vulnerable. Now the shaman starts casting Debris. He always says something when he is going to cast it and you can see where the rocks will land. You should evade those falling rocks, because they stun you for a long amount of time and they deal pretty much dmg. Now you just need to kill the shaman while evading the rocks and when he dies, the warrior will be vulnerable again. Just finish him off and that's it.
