Fast Cast needs reworked for RDM because of the way AF3 sets work, look at BLM, you have -12% cast on your head piece if +2, use this with a lv99 trial staff of an element and you have -26%, use with the neck that lowers it by yet another 3% and you have -29% with Fast Cast of /RDM you cast much faster than RDM will, I know a BLM who casts at about 18-20% which is faster than my RDM can using similar gear. I may not be meant to be a nuker better than BLM but the fact they can use their much more potent spells much faster than me is wrong, RDM has Fast Cast because it is meant to have the advantage of speed to it as well to make up for the lack of potency I would think, and as such I should be casting at least as fast as a well geared BLM, not slower.

As for Convert & Refresh not being lowered in potency its right, they aren't, I'm happy in a way my RDM need not cast refresh on all the mages in the party/alliance yet it also rids of some of the unique points of RDM which most jobs have nerfed unique points on them as a sub, also convert helps MP and gives much larger supplies which I would not change except perhaps making it to where half of your hp goes into MP, which would give you MP back still in a large amount wouldn't be so massive. Though it may lessen the effect of the sub-job itself would make it more balanced.

As for a RDM super-spell I think Amnesia would work well, stop the mob from using TP attacks for a short time with a high rate of resist build as to not allow locking its TP attacks all together, also duration would not be long, perhaps 15 seconds or so, enough to be noticed but not to make the enemy defenseless. Obviously NMs would resist it more often but not to the extent it shouldn't be used, it should have a high rate of landing on anything with the first cast, after that NMs build resist faster than other mobs would. For instance I can use it on high level worms in Gustav Tunnel and land 2-3 times if I so choose before it would be to resisted to be worth trying, where as in VW I would cast 1 time, and from there on the chances of it landing would be spotty at best. Amnesia is one of the most potent enfeebles against players (I would say the most next to silence which we already get, and muddle which has no use how it is against anything other than players) yet we have never had access to it, the only way I know of even for a player to inflict it is through WAR using the Great-axe with it as an additional effect. So I think it is fitting for RDM to finally receive one of the most potent enfeeblings in the game, and be able to restrict not only the TP gain of an enemy (which some jobs have already, RDM should have something to itself as a ultimate spell, not something other jobs have) but to be able to prevent it over a short period of time!