What other job in this game takes a DPS loss because they use a proc? None of them.

There are some major issues with end-game BLM and some very simple fixes to make it better that don't involve changing potencies or giving damage buffs. Having Fire 4 and Blizzard 4 increase the duration of their respective elemental phase ( AF/UI) by 2 seconds would be a major improvement. Making one of the thunder spells an instant cast would also be nice and not break anything.