The 23/38 build is an extremely strong healing build and it should in no way be "holding you back". The build is probably the most common raiding spec and most priests (myself included) heal very well with it so I'm wondering if your problems aren't coming from elsewhere.
As far as the build you have put together it's ok but I wouldn't take Lightwell. I have only seen it be useful in two occasions. One was in BM and the priest dropped a lightwell for the person handling adds. The second is in the Netherspite fight in KZ, a priest can drop a lightwell between Netherspite and the rear windows so when people run away from his bolts they can heal themselves up on the way to the windows.
Back to the big picture, unless you're guild already has a ImpDS priest you should not be speccing out of 23/38. If you do and want to go for an AoE build go for something like what is suggested in the FAQ or similar to what Schmere suggested.
Edited, Aug 23rd 2007 2:14:45am by MookusOU
Edited, Aug 23rd 2007 2:15:39am by MookusOU