I'm using the los trick as well.

The ranged don't shoot/cast through the walls, at least they don't for me. The key is to get everybody in the very front corner of the room. Back them up in there, including the tank. If you are having troubles with the camera being in that corner behind all the toons, back your tank in the corner and the swivel the camera 180 degrees. This way you can see the whole room.

At some point you will need to bring the tank out of the alcove because the casters will move back and keep casting. That's fine, at this point you can do whatever you like since all of the mobs are in the room. Just move him back as soon as the current wave is completed.

While I know you take a lot of damage from flamestrike, I still think it's better to just heal through it if you can, rather than running around trying to avoid it. The key to these types of encounters, imo, is getting shit dead, and moving around is counter to that. I know, so is lots of healing, but I think it takes less time and mana wasn't really an issue for me (keep water shield up if they are shaman).

No real clever strats needed on bosses, just burn them down and regroup after the fear. Yeah, tremor is worthless. WTF is up with blizzard and making every fight lately immune to totems?