You absolutely have to /sit in order to regenerate MP during the battle. If the other mages can handle keeping the tank and DPS healed run to a point VERY far from Ifrit and /sit so that you don't get caught by a surprise Eruption or other AoE effect. I learned this from experience (fought Ifrit 6 times in one night). MP regenerates pretty quickly when you /sit so hopefully this will allow any mages that need a quick /sit MP Break to be able to get back to the fight very quickly. Be sure to /sit in a safe place preferably as far as necessary to be out of range of any of Ifrit's AoE attacks because if you are sitting you will not be able to stand fast enough to get out of the AoE of whatever AoE Ifrit is using.