If only it's that simple. The crystals are stationary - they don't move, and there are 8 of them around Gelebron. Furthermore, there are 6 Sentinels that guard these crystals, they have tons of health, and enrages in 5 minutes.You can grab an add without agroing gelebron can't you? I'm too low lvl so can't try for myself, but if you freeze/bash gelebron, another player agros add, first player logs immediately after. Of course, that's only useful if those adds can be drained of energy in under an hour lol
If anyone can actually stay alive draining all the crystals without wiping to Gelebron and his Sentinels, then draining the crystals wouldn't need to be a strategy at all.