Having played Ragnarok Online rather extensively (both vanilla and Renewal), I'm of the opinion that elemental resistances are just a pain to deal with. The resistance chart in FFXIV's character screen is a leftover from 1.0 and they will not do anything with it. Changing the way resistances work now, after three years, would do nothing but confuse and agitate players. BLMs would either be extremely powerful or very useless, depending on how their "new" rotations would work.