Vampiric Touch - Is it worth it? (to ME?)

I haven't been posting much, but I've been playing. I've gone back to Alliance side (because my wife wanted to go) and I've been playing a new Priest (again).

So, I finally got my shadow priest up to level 50. I respec'd and got myself some Vampiric Touch. I've been waiting a long time to try out this spell, hoping that I would feel a sudden change in my mana usage.

I didn't. At least, it doesn't FEEL like I have more mana. Perhaps the mana cost and time spent to cast Vampiric Touch outweigh the benefits to myself to make me really feel it. I haven't crunched the numbers, but I still feel like I should just Mind Blast, then Mind Flay twice, and repeat.

When partied with my wife, she says that her Paladin feels the increased mana. So, I guess I'll keep it up when partied with her.

I tried to play Healer for a Mara group the other day, and I tried casting VT on mobs as she was tanking them. As it turned out, the mana cost to cast VT a few times really hurt, as I was down to 75% mana by the time I started healing. As a Shadow Priest, I already hurt for mana by the end of every fight, so if TV isn't bringing back enough mana to me, then I can't afford to cast it. I'm sure if I were playing as DPS in the group, instead of healer, I would feel much more comfortable casting VT, VE, and SW:P on each mob and not worry about letting the group die. /Sigh.

I don't enjoy healing a group as a shadowpriest unless I outlevel the instance. Simply put.