Rouse only buffs heals directly from the fairy. And fairy doesn't execute succor (if however u meant Fey illum healing 20% buff its a 2min cd therefore would not be up for each sequence; which is why i said sch could deal with this mech in several different ways but not the same way twice). so Succor is 150 heal 150 shield. If you succor the party before the photon erases everyone's HP down to 1%, you effectively have 150 potency heal on remaining on the party in the form of shields. If you're precasting into the photon mech you can fit 2 gcds in before whirlwind hits.If sch DOES NOT use emergency tactic to make their aoe all instant heals their successive succor will only heal for 150 potency since the initial pre photon succor shields is still in effect! so that 150 pre shield + 150 instant heal for succor + another 150 instant heal from succor + 400 indom. 150+150+150+400 = 850 potency.
Edit- Emergency tactic is a 30 sec recast... i was thinking 2min...... so that Sch 1150 potency.
You Could Add rouse to Whispering Dawn pre photon such that you get 2 ticks (6 sec) by the time whirlwind hits that would give you a total 280 potency rouse regen raid aoe. That would push sch to 1430 consistently timed potency.
Ast doesn't change much at all. You had synastry and that makes your 300 potency into 360 potency; light speed doesn't speed up your recast (however TECHNICALLY IF PERFECTLY TIMED even though it doesnt shorten your recast you might be able to fit an additional gcd inside that photon whirlwind window....but that's not reliable nor practical..and the recast on Light speed is too long). So ast still 720 potency.
So Ast + Sch = 720+ 1430 = 2150 potency.
But since we wanna add sch pre photon regens!! then we gonna add whm pre photon regens too!!!
so asylum 90 sec recast; 100 potency; so thats 200 potency in the 6 sec window. pre photon medic II with divine 65 potency, so 130 potency in the 6 sec window + whm already 1750 potency 2 divine+cure 3's + assize; for a grand total of 2080.
Compare how one healer (WHM) is comparable to consistent cd rotation AST + SCH aoe healing!!
2080 and 2150 are about the same....
NOte: there is NOT 6 sec inbetween Photon execution and Whirlwind execution; I just simplified to fit an additonal regen in the mix but the more technical comparision would be only 1 regen tick . So AST + SCH= 2010; and WHM = 1915 which introduces a bigger gap but still not huge!
NOTE 2
Note this is an example of content design that neglects WHM's superior healing abilities, b/c the Photon+Whirlwind sequence is so infrequent (AOE in general), and The number of utilities SCH/AST has are innumerable. SCH/AST has at no time need to be able to match WHM's instant/regen healing abilities. SCH/AST can use a combination of utilities to facilitate the necessary eHPS EVEN if its a different combo of abilities each go around. They will always have SOMETHING they can combine together to get the job done.
Moving forward if SE continues with the same philosophy behind the healers and similar content; one way of balance would be to render WHM pure healing effectively = to SCH utility. This would make SCH and WHM interchangeable since everybody wants that increase in dps late in patch; but this would also make SCH/WHM even more preferable during early progression over AST/WHM and AST/SCH (which are the two setups that would prevail later in the patch cycles).