I have no problem with fissures and no AoE. I have three level 20 characters, and only one of them has AoE. CC helps, especially for the adds. It basically boils down to conserving your resources and kiting the big guy.
Correct, @Medwin, yet the principle is valid; every 1 v N encounter has the same problem set. However, the difficulty of the game and the power of the player both go up together throughout. The problem is probably a difficulty adapting to this and/or a lack of well developed execution skills--perhaps the OP might have leveled with a group and so hasn't developed the necessary skills. Solo strategies require a different kind of skill.