@Marrakech you are nothing short of a fool... honestly if your "mana battery" is the only reason you feel you have a raid spot and consistently sit at 14th-15th in dps you just outright fail. With the exception to heavy aoe fights (where spriests fall behind due to lack of aoe) I have ALWAYS been in at least the top 10. I NEVER chug mana pots and at most use 4-5 a night raiding. Anyone suggesting you must chain mana pots either has a horrible rotation or your damage is to low to be effectively using VT anyway. The only time I ever had some mana issues was after i went over 1250 (unbuffed) shadow dmg and started gemming and gear toward haste and got up to 65 haste rating or 4%. Even then on a mulitple mob boss fight I'd use shadowfiend twice and pop maybe 2 mana pots, and oh yea I come out #4 in dps. I will admit 3 dps are undergeared, but still if your coming out something like 14th-15th ie behind or even to tanking dmg or need to chain pot don't blame spriest design, blame yourself. Over all if you are doing that poorly you don't even deserve a raid spot for VT, because another class could dps better then you and in the end would serve a a net conservation of mana for the entire raid.
It may very well be your gear level vs your raid, but it's more likely either you dont have enough hit, your dmg is far to low, you are refreshing your dots to often, you aren't using SW
every time its up (assuming you aren't already taking heavy dmg) or your spec or rotation is just wrong. I played a lock since release and only raided prior to 3 months before tbc, pvped for awhile, raided and pvped early tbc finally switched to only pvp for my lock and then rolled the spriest for pve. Honestly the spriest does near as much dmg with a lot more utility and is MUCH easier boot when played right.
As far as dispersion, I'm not impressed for a 51 point talent, but I like it. Do I think it should be better for sure, but it's not horrible esp with potion sickness. As far as VT being nerfed so be it, i'd rather doing better damage without some silly tricks that so many classes are getting mana regen for party or targets etc and so much better personal mana regen accross the board. VT will just be a good bonus, that with the new spirit tap + shadowfiend + dispersion should make spriests have no mana issues.