Focused Mind? No Imp VE? He's already low on health, and you want to gimp his survival tools? Unimproved VE is one of the most pointless spells in the game. No, something like
this is going to serve him much better at 49. Since he's already low on crit and shouldn't take Shadow Power, I'd might have moved the Mind Melt points to Imp Mind Blast as well since it will be one of his highest damage dealers whenever he's protected by a group.
And to the 49er himself...
Yes, you are very low on health. Hit the Auction house and start getting things like of the Eagle (Int/Sta) and so on. Since you won't be relying on Spirit Tap, spirit has less use at your level in PvP. Starting out with a huge manapool and healthpool will do you much better since the fights will be fast-paced instead of drawn out draingames. As soon as you can, sit and drink/eat and get back up to full fast.
Also, I suggest hitting Shadowpriest.com to find the latest working TabDot macro. It will allow you to just spam one button to put SW:P on every enemy within range.
There's one thing I just want to share with you, though. I PvPed as Shadow at every single tier except 60. 19, 29, 39 and so on. Never dropped the tier until I'd picked up all the BG items I could (even though there's several PvE items that are better) as a Priest. I'm just saying this so the next paragraph might be supported somewhat by experience...
Don't bloody refuse to heal! You are a Priest, no matter what color you are. Popping out of Shadowform gives you access to a whole range of wondrous things like Renew, Flash Heal and delightful group heals. Never stay inflexible, since BGs are
teambased. Unless the team wins, you are a bloody loser no matter how many kills you rack up, and unless there's another healer present you'll just have to face the facts. Which is that you will do more good outside of Shadowform healing the group than staying in Shadowform melting one face while your teammates are dying all around you. However, if there is another healer present, stay in Shadowform. You'll be DoTing everything around you, doing massive damage while slowing flagcarriers and fearing enemies. When there's other healers present, you are definitely worth more as a facemelter than backup healer.