It's a nice start but it feels like there is a way to go still.
The main problem with the UI is not layout (which is all good and fine), it's that there is a lot of information overload going on. A common response to that criticism is "I like to have all the information I need available to me", but the point about overload is that I can tell you a large chunk of the information on your screen is not needed to heal a raid at any level of performance, and the information you DO need is not afforded the required prominence for all the other stuff in the way.
Think very carefully about what information is actually going to influence what buttons you press during a fight. As such things like "+688 Mana [4 hits]" are totally useless. Combat text, scrolling or not, is pretty useless for a healer. The cooldown notifications are the only functional bit.
Your buffs can be separated into passive and active. Passive buffs are things like MotW, active ones are things like Serendipity. Active ones should have a salient location with clear duration shown, passive ones can be tucked away with only very approximate durations. You don't need to know other people's debuffs on a target either, unless you are raid leading a raid of casual raiders who aren't sure of what they are doing.
There is a bit of text overload on your healing frames too (the numbers aren't needed, just react to how long the bar is) and the text seems to be overlapping the buff icons.
Your boss mod needs stipping way back. On screen you have:
1) "Call Blood of Shu'ma on purple, green, black, blue"
2) "Yor'sahj the Unsleeping calls upon the purple, green, black and blue Bloods of Shu'ma"
3) "CALL BLOOD OF SHU'MA"
... you only need the first one.
Also, half or more of all boss mod warning are not relevant to any one player. Switch them off, they're not for you.
Sorry if that seems overly critical. I know you say in your comment it is a UI for DPSing also, but most of my comments hold true for that also.