Really? We are only doing 300 more dps than prot warriors on beta at the moment.
Do you actually have a beta account? Prot warriors just got devastate nerfed, and shadow priests do slightly high dps. Complain about our replenishment being overly clunky if you want (even tho a normal spell rotation should still cause it to be up 100% of the time) but the dps is fine.
I think the reason they introduced the MB component was to ensure the replenishment buff wasn't constantly being reapplied too quickly. For example, if the replenishment buff was to reapply on all shadow damage, i'd suggest it would be doing so just about every second while the spriest was dpsing. My SCT is constantly reporting damage numbers from VT, SW:P, MB, SW & MF... in short, spriets do a lot of small amounts of damage very quickly. That would have triggered replenishment refreshes at a pretty stupid rate.
Same situation (on a lesser scale) with just having it on VT ticks, im not sure a refresh every 3 seconds is a good thing either and it's probably open to abuse in that a spriest could just put VT up and have 30seconds of refreshment for 1 VT mana cost. (15 sec refresh buff, so last tick would have it last 15seconds after the effect ended). I guess that they want the spriest spending resources in order to keep the buff up for that length of time. Is that necessary? Not entirely sure but i'm sure someone more clever than me would find ways to abuse it otherwise.
I guess by introducing MT to work with VT it means replenishment won't refresh any quicker than 7 second (5.5 CD + 1.5sec cast less any haste but thats gonna be less than 0.5 seconds) which makes a bit more sense... while it fixes problems relating to the refresh happening too often it's now a somewhat clunky mechanic. Not sure I can think of a better idea that simplifies the mechanic but overcomes the refresh occuring too often. Obviously they want VT to retain the mana regen mechanic as it's the 41 point talent that introduced it in the first place and that just makes it more difficult to find a fix.