Doesnt have to be mages to click the tube... anyone can click the tube after the "rain" aoe hits.
U should have ur healers and bards what ever is in your group click AOE blockers on Inc when u get the red text for arcane your Mages must click the arcane protect tube atleast one mage has to click IIRC = )
seems easy enough
We've never had any appreciable wiggle on these timers either. They are some of the most reliable in the expansion.
Must be lagging. The timers are all 40 seconds on this mob.