Yeah, it's a pretty bad build for raiding. It might cut it in heroics, and you might be able to get away with it in raids if no one inspects you, but you're missing some vital talents.
First, you're missing your clutch talent. You know, your go-to spell for oh crap moments and predictable incoming large hits. For discipline it's Pain Suppression at 41 points, and for holy it's the 51 point Guardian Spirit.
Without one of those, especially in 25 mans, you're missing about a third of the reason you'll be picked to fill a raid slot as a healer. Unfortunately, healing isn't the only reason you get picked for a raid, and you seem to have missed the memo.
Second, you're a holy build, but you don't have Circle of Healing. Yes, as you feared, you need CoH because Holy is a priest's raid-healing tree. Raid-healing is what Holy priests do that sets them apart from Discipline priests. You didn't think you earned a spot with improved death alone did you? As a holy priest you'll be brought to a raid because of Holy's ridiculous healing throughput. Between CoH and Prayer of Healing you'll bring more group-level heals to the raid than any other healer in the game bar none. All on demand; all immediate; all heavy hitting. Resto shamans cap out at three targets per cast, and druids have to wait for their healing to take effect. If an entire group is about to die, you want a Holy priest to pull them out of the fire (or to just make sure they live long enough to run out of the fire depending on the boss).
In a similar vein you don't have Light Well. Some priests love it, most priests hate it, and yet more are indifferent. As a warlock (on top of a priest) I personally like light well as it allows those of us with a mind towards self-reliance, who don't like to be a burden to the healers if we can help it, to take care of ourselves. Recent buffs to Light Well also make taking a second look worth it as it is the single largest healing per mana in the game bar none. The second place contender is so far behind it's not even funny. It's total value is a toss up and greatly depends on the individual raid, but you specifically skipped it which makes it worth mentioning.
Finally, Disc is not better than Holy. It's different.
Discipline excels at single target healing, damage mitigation, and longevity.
Holy excels at raw throughput with group healing (if you count the shield from Divine Aegis Discipline's heals hit way harder than Holy's do given similar gear).
If you care about healing meters (hint: you shouldn't. They're inaccurate and don't actually display useful information at any time. Ever) then go Holy and don't look back. Go full holy too. Not anything related to this disaster of a hybrid build you've got going.
If you want to specifically tank heal (you'll always have a job. Most priests I know are Holy and Holy paladins have been in astoundingly short supply as of late for some odd reason) then go Discipline all the way to Penance and make sure to pick up a good single-target clutch rotation while you're at it.