Ok, I was about to go quote happy with a bunch of these, so instead I'll save myself and just post my overall opinion on this.
LS's preffered Order: WHM > DRK > BLM > SCH > SMN (NIN and BLU not listed because this is a generalized view)
Personal Flavor (for myself): SCH > BLM > WHM > DRK > NIN > BLU > SMN > BRD
The first group is what Leaders will look for in shells. Rarely do leaders let RDMs tank, unless they themselves are RDM tanks or have let it happen and enjoyed the results (or just to appease them if they whine at them enough).
Second Group, I'm what you might call old fashioned. My RDM has been 75 for going on 5 years. I come from when Refreshing, Enfeebling and Nuking on MBs was the RDM's primary job, with Curing and Hasting when the WHM needs help. This being when it was Tank/SC DD/SC DD/WHM/RDM/BLM was preferred (maybe swap WHM or RDM for BRD). So BLM had always been my preferred sub. WHM, makes sence to be among the top. I see SCH as less situational than DRK and I'll explain why below (though DRK is for one reason, Chainspell + Stun, so keep that in mind). NIN is mostly for soloing, makes Ifrit and them a breeze. BLU is great fun in ballista and has similar uses outside that as well (I solo'd two well geared PLDs at the same time, without using silence, between Phalanx/Cocoon/Stoneskin they never got me below 90-95%). Outside of carby pulls, no use for SMN. The magic and abilities of all jobs before it very much outweigh the auto-refresh and extra MP. BRD doesn't give much of anything but low level BRD buffs, of which Mazurka and Ballad are nice but 2 spells vs all the others from above.
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Ok, now onto the controversial subbing SCH. In situations where Cursna and/or Erase are paramount, SCH doesn't work out. Same with ES, Sleepga or Stun. Reraise can be purchased via meds/conquest(or similar)/AH (rr earrings/gorgets/hairpins). Having been a RDM for so long, and having SCH to 71 (as of last night) I have to say that SCH is imo the better sub for overall utility and flexibility, which is what a RDM excelled at for all these years.
You can have a sublimation charge before you reach camp (a free ~250 MP). You get the discounts on MP per the arts, and lets not forget the stratagems to help out once in a while (gogo 44MP Cure IVs or 75mp Raises, or the recast time cut in half). Sublimation is comparable to refresh in this regard: Refresh gets you 140mp after spending 40mp. In the same amount of time as a Refresh from start to finish, Sublimation can charge up around 100mp. Refresh only wins out on the angle that there is no 30 second timer to start the next cycle.
For RDMs fortunate enough to have Duelist's Capeau and a Refresh Body (especially if both), Sublimation would be more beneficial as you otherwise have a means to regain MP without resting to help offset casting spells.
Light Arts: with Addendum: White covers you for all WHM excluding Cursna, Erase and Reraise (spell). It also will improve Healing Magic Skill as RDM falls below B+. Now admittedly here, erase plays a huge role in many events, which is why even I place WHM above SCH still overall.
Dark Arts: while there isn't any change in the way of spells, times requiring Black Magic skills outside of Enfeebling Skill, this works very well. You can afford to use more MAB gear for nukes (I can push above A+ Ele skill with /SCH and Warlock's Chapeau, AF2 legs and Ele torque). You also gain Drain and Aspir and some skill to back them up. Between Bio II/Bio III (with merits), Dark Arts, Crimson Hands and Dark Torque, you can pull off respectable numbers (keep in mind that Bio DOT is Dark Magic based, not INT).
I'll also note that ES is a guaranteed way to land (if it can land at all), but for a RDM, most of those things we can land without it. Good examples are: Brothers (usually the big one is ES slept, but Tomasello and I have both slept that mob w/o ES), Azure Expiriments I personally have a 75% success rate without ES. But we also tend to have little to no problems pulling 1 mob at a time. Even on Kirin, most RDMs can land Gravity readily as long as they don't over use it, thus allowing it to build resistance.
Anyhow, so that's the angle I see it. You gain a lot more by subbing SCH than any other jobs in terms of overall flexibility and in several cases, capability. Unfortunately some things just can't be done without, namely Erase. Almost everything else can be replaced by items or a skilled player especially if they have gear to support them.