Time to start complaining about things that don't even exist yet.
Things are still in alpha so it's a little too early to complain about the particulars of anything from Cataclysm, but its the very best time to complain about the general structure of things. Basically however mastery looks when we get to the beta is probably how its going to look when we get to release and when we get to the next expansion. The numbers will get moved around, but the basic premise of how you get mastery will take a huge amount of effort to change.
When we first heard about mastery it was a passive bonus attached to every talent point. More talent points means more bonus. Since then we've seen how this concept has been refined. Basically its refinement has dealt with some fairly obvious problems.
Problem: People will be encourage to spend all their talent points in their chosen tree regardless of whether they want those talents just to get the passive boost. A retribution paladin will, for example, want to spend all 71 points in retribution since those give a damage bonus. In this way, mastery will lower choice instead of increasing it.
Solution: Put a cap on how much mastery bonus you can get from a tree. Only the first 51 points give you the bonus.
Problem: Classes that have multiple trees that perform essentially the same function will be able to "double-dip" mastery bonuses. Any mastery bonus you could give a rogue, for example, would be good for a rogue of any talent spec.
Solution: Only give people mastery bonus from the tree they put the most points into.
Since then people have raised some other problems. The mastery system will mean you need to put 51 points into a single tree and so will essentially kill hybrid specs. Another issue is from a new player perspective. You hit level 10, you say, "I want to smite people with awesome holy power" so you look at retribution. Sure, the talents don't appear to make you better at smashing faces, but that's okay, there's that mastery bonus at the bottom of the tree. So you click your point and you get... 0.156% extra damage and 0.392% extra holy damage. You might be a little unimpressed.
The solutions proposed for these appear to be to say, "Who cares about hybrid specs anyway?"1 and to not realize the second issue is a problem at all.
I have a two stage solution to both problems.
The first stage is to put mastery on a non-linear scale. Since you only get mastery from one tree, and only the tree you've spent the most points in, you don't have to get the same amount of mastery for every point you put in. Instead of the first point giving you just under 2% of your final mastery bonus, it could easily give you around a third of it. Imagine if that first point gave you 3% bonus damage, healing or damage reduction. At that point you wouldn't wonder what it did, you'd know what it did. Your talent choices would help to define your character's abilities from the very first point. This would also prevent the system from punishing hybrids excessively. If you get to 80% of your final mastery bonus for putting 30 points in the tree then you will be closer to a full master bonus if you split your points three ways.
The more extreme solution, and the road I think they should probably take, is to build on what I've said above but base mastery bonus on level rather than on talent points spent. Talent points would only determine which mastery bonus you got. This would completely eliminate the senseless penalty to hybrid specs. It would also provide a very meaningful and noticeable way to reward advancement because mastery bonuses could be awarded in steps at certain levels rather than in tiny increments. You could even put achievements in (achieved rank x mastery) to let players know that their mastery bonuses had increased. The mastery system, since someone dreamed it up, has gotten further and further from adding a passing bonus to all talents, might as well go whole hog.
I would put the probability of my second solution at extremely slim, but there is some hope for the first one. Suggestions forum, here I come!
1. If hybrid specs don't matter and specs aren't really specs until you put in that 51st point then why does Titan's Grip need a 10% damage penalty?