*ADJUSTMENTS MAY BE NECESSARY*
That is the sequence of events after the first crystal clear which should be done by two fairly equal groups in sync. After the last 2 crystals are cleared you will want to return to your starting positions as shown in the first picture, and repeat until Gelebron is dead. We don't know what happens throughout the raid, whether he gets harder the further you get etc. I suggest using this as a template if you have no idea how to begin, or have no real idea in place.
This is my vision of the encounter and this is the plan my clan would have liked to put to the test, we just want to have a fourth druid levelled for reasons said above. Hopefully this will help those worlds that have the numbers and lack a good strategy. I see no reason to keep it from anyone. Good luck.