A lot of classes are pretty upset about some of the changes we've seen in beta build 8926. Shamans are dot shocking (what else is new), I'm complaining about Holy Priests (ditto), etc. In short, there were a lot of nerfs. Ghostcrawler has emerged to let us know that indeed, there were a lot of nerfs, and there's a reason for it: talents have a budget.
You may be familiar with itemization budgets. Basically, an item of a particular item level has a certain amount of "points" to spend on various stats; if you want to load an item up with Stam, it's not going to have as much to spend on Agi, for instance. This is also the reason why caster weapons have low DPS, because they borrow points from weapon DPS to spend on stats like spell power.
Similarly, talents have a certain amount of power that they're budgeted for. As a specific example, GC stated that "we have an idea for example that a talent point should be worth around a 1% dps increase," which was really nice to see because this has been a personal benchmark of mine for a long time. Some talents are under this and tend to be viewed as filler, and some talents are far, far over this and tend to be viewed as mandatory. This pass was intended to balance that out to a certain extent, to tone down the talents that were just stomping all over the other ones.
GC goes on to clarify that this is not an class-vs-class balance pass. They don't have the data yet to make sure one class is as good as the next. And of course the best thing to do, if you're in the beta, is go out there, test, and give feedback. I do think that a lot of things were over-nerfed, but that will probably become clear enough soon.