At risk of posting something HELP I AM TRAPPED IN 2006 PLEASE SEND A TIME MACHINE, I'm going to summarise what I feel are the problems with RDM at the moment and how to fix them (this may not be possible under the current system but regardless);
RDM's main problem is an identity crisis. It is supposed to be a jack of all trades, but SCH competes with it on this role. It is supposed to be a major enfeebler, but immunities and the small increase of tier1 enfeebles vs tier2 enfeebles render this largely obsolete.
Therefore, what I would propose is this:
Stop making RDM a jack of all trades. Turn it into a support mage and allow it to grow into an entirely new role.
Change #1, global across all jobs with access to the spell: allow Haste/Refresh to be maintained persistently for some upkeep of MP (slightly higher than now to accommodate for the casting MP to maintain it previously). Shift gameplay away from maintaining basic buffs and towards activity.
Change #2: turn RDM into a proper melee/mage hybrid. I have never been an advocate of melee RDM while playing since the implementation is entirely halfassed; RDM cannot be a high power DD due to balance reasons, so
it meleeing must perform some unique role.
How to do this? There may be balance problems associated with it but:
Two stances. For lack of better terms, Melee Support and Mage Support. Melee Support can increase the effectiveness of buffs applied in tandem with damage and other effects (as well as perhaps apply new ones depending on what you do such as a somewhat weak but stacking Stoneskin and such?) and Mage Support can increase the effectiveness of debuffs applied, in tandem with damage and other effects (eg: increase potency of Slow in tandem with earth elemental damage inflicted).
This would allow RDM a more dynamic role and give it a proper place in a fight (imagine if you could slightly increase Haste potency etc)! Basically, make RDM a true support class able to adjust to a given situation and shift the gameplay away from buffing and more towards pro-activity.
Change #3: finally, to address RDM's curing issue while keeping the flavour of the class intact, give them access to a JA with a low recast (~30s?) named Doublecast. Cast two spells at once for 2x (or more) the MP cost of a single cast. This allows RDM the ability to cure in a pinch while remaining well below the level of WHM in terms of healing (note I am proposing this knowing that CureIV's potency is going to be increased).
Problems: I know this is intruding on DNC a little bit, since they are supposed to be the ones who turn melee damage into healing/debuffing. Simply amplify DNC and allow them to provide different kinds of debuffs (as they do) and remove the shared Waltz cooldowns FFS. Finally, perhaps add something like a buff which you place on one person who cannot be yourself where they heal a certain (low - not to the point where you can replace a main healer but just to provide supplementary healing) % of the damage you deal, and only allow one DNC's buff to be active on a single person at any given time.
SCH may need some buffing to compensate for this but this is easily handled via strategems.
I've probably just been playing too many other games lately, but I feel FFXI's biggest problem is that it tries to homogenise its classes too much, which is to say a healer is a healer, a DD is a DD etc. If you make every class offer something different, you end up with better synergised gameplay and not just "I want a DD? Okay, WAR/MNK it is".
The proc system is an attempt to increase class diversity but it's one which inflicts inconvenience on the player. I think allowing each job to have a more unique flavor and their own niche is best overall.
But I could be dumb :)
I dunno why I typed all of this.