If you can have 1 new Off-Global cooldown skill.....

[Nihonnick]

AST
combination or deuce Recast - 240sec
Repeats your last drawn card.

dead hand or renounce Recast - Instant
Removes a card from play till used again.
So if you dead hand Bole, you will no longer draw Bole cards.

sans prendre Recast - 300sec
If you play a card without using redraw (also does not affect held cards) It's effect is doubled (like Enhanced Royal Road) Will also be affected by - Royal Road (aka can Enhance a Expanded Royal Road Balance)

spread Recast - 300sec
Will spread your next card played. Will also be affected by - Royal Road Skill
(aka can spread a Enhanced Royal Road Balance)

revoke Recast - 420sec
Will remove all card effects in play, to enhance (card drawn), expand (cards on party members), extend (royal road waiting to be used)

So if you have a expanded card in play, a card drawn (does not affect HELD cards) and a royal road buff active, your next card will be Extended, Expanded, Enhanced.

Some are maybe to OP..

[Vincent_Mateus]

Dragoon
Svipul: Single target jump that consumes all of BotD timer.
OGCD
150 potency + 10 potency per second remaining on BotD.
30 second C/D.
Not affected by Power Surge.
Removes BotD buff.
(Animation Lock as long as Jump or less.)

[Nora_of_Mira]

Dark Knight
Grit is now an OCD instead of a GCD.

you have no idea how much I want this. please make it happen.

[Daranion]

PLD
Saint's Cross
2 Strikes with 200 Potency Each
Adds 280 Potency Regen to self on cast and Cleanses Debuffs

[Kazrah]

While whm may win in raw heals and dps, Sch excels at Dpsing while healing. First and foremost, the fairy delivers a 300 potency heal every ~2.5s (maybe less, haven't looked at my fairy spells in awhile) as well as Adlo, succor, and the ability to Lustrate quickly then right back to dps. On top of this, whm has far more trouble in the mp department, particularly while dpsing. This is why sch is excellent as an off healer.

So first off, the fairy's recast timer is 3 seconds, so it's actually slower than a regular heal on top of being weaker. It's also because of that fairy that players tend to fall for the illusion that SCH has an extended time dps'ing when in fact WHM periodic healing effects (Regen, Medica II, Asylum) allow for just as much dps uptime, if not moreso since those hots can easily outheal whatever a fairy puts up and for a longer duration. Add onto that skills like Tetragrammaton and Benediction, and WHM can fit a supplementary healing role just as effectively as any SCH can.

Secondly, the fact that you're using the term "offhealer" is all the more reason why it should have ET as a stance: because that label shouldn't be permanent on any job. Much like WAR and the term "offtank", every essential-role job (a.k.a. tanks and healers) should be able to fill a primary role-based position just as easily as a supplementary position. The only difference is that no group has ever been at a disadvantage because it had two WARs (hence their tweaking for Stormblood).

The only real thing SCH has an advantage over WHM is utility. Where SCH brings things like group-wide damage reduction, WHM only brings more healing power and slightly more damage. If anything, WHM needs more utility components like that, but the real hurdle is trying to get it in while still fitting that "pure healer" theme WHM has always carried.

[Paladinleeds]

Warrior
Unburdened Rage
15s duration, 300s cooldown
Duration between auto-attacks and GCD is reduced by 90%. TP regen is mildly increased (so the Warrior runs the risk of draining his TP badly, you use this when you have full TP else you're likely to drain your TP to 0).
After effect ends, 15s non-dispellable Pacify, Amnesia, Silence, and 90% slow (think of it as the Warrior needing time to catch his breath after unleashing his fury), plus auto-attacks are disabled for that 15s duration.

[Vivi_Bushido]

Bard
Freedom Fighter
20s Duration, 180s cooldown
Enables Auto Attacks and removes all cast times while in The Wanderers Minuet. The additional DPS gain from the The Wanderers Minuet stance remains unchanged. Can only be used while The Wanderers Minuet is in effect.

[Gemina]

Scholar:

Divine Barrier
Cooldown = 600 seconds
Duration = 10seconds
Effect: Next adlo cast will crit

White Mage:

~Already mentioned~
Osmose: MP recovery
AoE Esuna: Removes one detrimental effect from all party members. (not all effects can be cleansed)

[Hayward]

Summoner:

Astral Flow
Duration: 30 sec
Recast: 5 min.

*Triples potency of pet's attacks (Including Enkindle)

[Skivvy]

WHM - Esunaga
Cooldown: 120 seconds
Removes all status ailments on party members within range.

This would make me a very happy WHM.