Whm/Pup is a possibility later on, If your main function is healing only. But even then, certain mobs, you want to cure spam, and a cure 4 every 18-20 secs, may not be enough. If you want to enfeeble, it won't help you, if you are not low on HP, it won't help you much, and pets have the uncanny ability (especially pup) to cast cures over your regens, which when players do this, it drives me nuts.
As far as /Rdm or /Sch as Drakonite said, its going to be a toss up, so have both leveled.
/Sch will offer Stoneskinga, Blinkga, Aquaveilga, Regenga 1, 2, 3, Drain, Drainga, Aspir, Aspirga, Additional Stratagems to reduce Mp cost of spells, or cast and recast times, Conserve MP (which is just icing) Resist silence, Light Atrs 10% cost and cast time reduction and Sublimation.
/Rdm will offer Refresh, Convert, Phalanx, Gravity, Bio 2, Blind, Bind, Poison, Sleep 2, Enspells, Blaze and Ice Spikes, Fastcast and Resist Petrify.
Alone Refresh is "better" then Sublimation. Sublimation offers 2 Mp a tick up to 25% of your Hp (not taking gear into consideration) so for a Taru with 800 Hp, 200 Mp every 5:30.
Refresh gives 150 Mp every 2:35 (5 sec cast time) typically not recast until it wears off. Refresh costs 40 Mp, so net is 110 Mp over 2:35 or 220 Mp over 5:10.
Convert is ~ 800 Mp every 10 mins. Now, obviously convert and Sublimation will vary based on race and some gear. I am just useing these figures as an example. However Tarus actually have the Least efficient Sublimations, since they charge the shortest ammount of time and hit the 30 sec buffer more often than other races.
In terms of straight up MP regeneration, /Rdm wins out. But then you have to look at Mp useage. In this Dept, Rdm offers nothing. While Sch offers a straight 10% cost reduction, Conserve Mp and 1/2 Mp cost stratagems.
You also have to take Aspir and Aspirga into account.
Its going to probably come down to a matter of personal preferance, and will be situational, each will preform better in different situations, while skilling up, /Rdm will probably be better, due to more staying power, more enfeebles, Phalanx (take less damage, live longer), Where /Sch will be better for events, where you'll need to raise people fast and where you can aspir mobs, like Campaign and Dynamis, basically, where you have time to get Mp back.
Level both though, you will want that at least.
Chocobo Status: Retired Green, Black, Red, Yellow
Whm/Blm/Rdm/Mnk/Thf/Pld/Blu/Smn/Dnc/Pup/Bst/Drg 99, War 91, Brd/Sch/Sam/Nin/Cor/Drk/Rng/Geo/Run 60
Alch 72+1, Cook 66, CC 61+1, Wood 61, Synergy 56, Bone 54, Leather 51, Gold 49, Smithing 45, Fish 15 http://ffxi.allakhazam.com/profile.xml?143946