It's a big red flag to me that as disc, his top spell is PoH on many fights. He usage of atonement is abysmal at best. I suspect his gearing as disc is likely not correct either, looking at the very low DA generation. He never seems to make any use of Inner Focus either, or Spirit Shell. And when he does he isn't using it effectively (ie 5% of his healing on Thok).
He's using Glyph of PW: Shield which really, if I could... oh I'd delete that thing from the game.
As Holy he's taking Power Infusion instead of Divine Insight. He needs to be taking Divine Insight most of the time, it will provide him with some burst from PoM. Though Twist of Fate is also very strong, and can be considered in very stacked fights where PoM just isn't going to be bouncing, or in fights where he can game the uptime (SW: Pain will trigger is, even as holy). ToF is always the go-to this tier as Disc, except when heavy tank healing (then he should take DI) for fights like Dark Shamans (though I take ToF here too).
As both Holy and Disc, he tends to use Divine Star haphazardly, not really getting it's full potential.
I can understand not using renew often/heavily, and perhaps favoring AoE Chakra (blue / Sanctuary) but to see absolutely no Serenity spells being used is concerning (Renew, HW: Serenity). He doesn't seem to be using FDCL either which is really going to hurt him. In 10m especially, being able to roll FDCL procs (free instant FH's form other healing spells) into Serendipity is going to really hamper him. IE his spot healing is very weak. He should learn to favor a stance without gimping himself -- ie knowing the encounter and knowing when he'll need to switch Chakra's as the CD is punishing.
You're better off, IMHO, staying in Serenity in 10m, and gaming FDCL / renew usage blanketing and abusing your level 90 priest talent, and then planning to be in Sanctuary for stacked healing phases where everyone will be taking damage. It's easier for me personally to plan around big periods of damage, but that could be the disc in me!
Overall I see some serious glaring flaws in his understanding and implementation of his toolkit with both specs. I'd point him this direction:
http://howtopriest.com/viewtopic.php?f=13&t=4484
Update:
Creeped on his gear.
17k spirit? 7k haste?
He's just throwing stats around and I'm not entirely certain to what end. He should reach the 2nd renew breakpoint, or the 1st (so 4721 iirc for 2nd bp, of 3039 for the 1st, favoring the first if you use less renew), and dump the rest into mastery/int. I can't imagine needing more than 14k spirit as Holy, maybe 15 without the meta. I've done fine with 10k with the meta, but I'm insane and also don't heavily use renew/serenity and instead, lean heavily on EoL mastery.
He ignored a mastery bonus on his boots, which makes me nervous.
He needs to be gem'ing int/spi, int/mastery for holy, or spit/crit, int/crit, crit for disc.
Also, iirc, glyph of PoM is a healing loss. He should probably change that glyph out for something more useful (I prefer Glyph of inner Sanctum/ Glyph of Fade for some defensive's).