to be honest i wonder why the healers should swap at all. healers already have to concentrate a lot in this fight so the dps should not be that lazy and just check which healer has the debuff. and ifrit anyway turns either to left or right when he is giving the debuff so the dps for sure should be able to see it easily.
like this the healers are always on the same spot and they just have to swap once in the last phase. the less a healer has to move the more he can heal. never forget that. and dps rly does not have a hard job at ifrit....