It is purely line of sight and positioning.
I go up there to do my raises during that fight, so the peeps are safe for a few seconds whilst I get them back up to speed.

It's not totally broken, because if the tank dies, and Terasaur comes up to you in that area (pillar or not) you get doom.

So, I guess no worse than avoiding an aoe...standing somewhere it doesn't hit you. That's all.

If you were immune to it up there, then that's different...but it's kinda a safe zone. Like I say...I jog up to that area to do my raises (if needed)