See thats what a lot of whms see us and sch as, competition, sch and blm see one another as nuking competition (to a degree mind you, and while sch cant nuke harder, with good strategem use and timing they can self skillchain and magicburst with nukes.) But as it stands, just like some rdm state, cure V will not replace whm, can it in some situations? Sure! All? Nope! A lot of people talk about spell economics in ffxi, so i will too.

Rdm/whm Vs Whm/rdm Vs Sch/rdm
Curing power:
-Rdm: in this setup at 90-95, rdm gets 4 native cures, and 3 aoe (curaga, curaga II, curaja) as well as 2 regens
-Sch: pocketing 4 full time and 3 regens
-Whm: cure 1-6 aga 1-4(5), cura 1-2 and 4 regens, as well as more potency gear AND Solace's stoneskin effect.
Summary: Even getting Cure V, whm has a whopping 4 more types of curing, solace's skin, and potency gear to overshadow rdm/sch cure power (whom at most if i read right can get 43% if they use every augmentable piece of gear for it)

Buffs:
-Rdm: Protect/shell 1-5, regen 1-2, enspells(self only) Bar-element/status spells(self only,) Stoneskin/blink/aquaveil/phalanx/gain-spells/spikes(all natively self only), refresh 1-2, phalanx II, Protect/shell 1-2(3 protect at 90 i believe?), and haste.
-Sch: Protect/shell 1-5, regen 1-3, tier 1 enspells, refresh, stoneskin, aquaveil, blink, spikes, bar-element and status, regain, hate up, hate down, Stormsurge storms, Klimaform.
-Whm Protect/shell 1-5, protectra/shellra 1-5, regen 1-4, auspice, stoneskin, blink, aquaveil, phalanx, refresh, Boost-spells, haste.
Summary: Okay, shorter list, but right off the bat, you notice, that aside from a few odds and ends like haste, theyre all single target and most natively not offered to other jobs without accession, while white mage can do the ones we can normally cast on others (sans haste) better and for less mp, when it comes to spell economics, buying in bulk for a discount beats saving 10% on each unit (60% savings after it all vs Apx 500% savings if you are casting on 6 people.)

Debuffs:
-Rdm: Sleep 1-2, poison 1-2, dia/bio 1-3, para 1-2, slow 1-2, blind 1-2, flash, break, gravity, bind, addle.
-Sch: Sleep 1-2, poison (maybe 2/rdm?) dia/bio 1-2, para, slow, blind, break, gravity, bind, and lets lump in drain/aspir.
-Whm: Sleep/repose, poison (maybe 2/rdm?) dia/bio 1-2, para, slow, blind, flash, gravity, bind.
Summary: rdm asnd sch are virtually in the same boat as whm.

Nukes:
-Rdm: Tier 1-4 Banish 1-2 Banishga 1-2.
-Sch: Tier 1-5 up to aero (Blizzard after 95 update)
-Whm: Banish 1-3, Banishga 2, holy (holy II after update) Stone-Aero II
Summary: The only field where whm loses out, and personally ive yet to gear MAB gear on my whm to try and see how high i can nuke /rdm or /sch, but ive landed 1.2k holy and if holy II is anything improved over that, its plenty for a good kill-shot.

Overall: Cure V will make rdm/sch sufficient healers in a single target situation, it will not retire whm, just add competition.

Personal note to the white mage croud: You know whats worse that rdm and sch getting cure V? a massive influx of new whitemages gunning for all your whm specific gear and spot in events. Just let that sink in a bit.