Quick question on Cithrells Fall

Just a quick question on The golem boss here ..

I know the mechanics of this fight - all of that is fine. But I wonder if anyone knows the details of the damage from the void zone things...

We were doing a Cithrells 31 yesterday and when the boss was at 50% health, each tick of the pulsing aoe was hitting for 120k-180k on the party. Now part of me wants to say this is an enrage mechanic and our DPS was just too low, but just trying to make sure we're not missing something else... I checked the logs of some of the 37 Cithrells and they were taking avg of 40k /max 80k from it, so either were missing a mechanic or the dps was just lagging a bit.

Yes, everyone was using magic guard and/or the aoe dmg reduction, and DR weapon defensives.