Blizzard is once again doing some stat adjustment for Mists of Pandaria. The whole article is
here, but I will list some of the major changes.
Resistances have been abolished. They felt that with the way the game was moving they were not utilizing the mechanic, so it just was adding another set of confusing stats. As such, spell penetration is also being abolished. They have not explained what this will do to racials that increase resistances.
Hit and Expertise are being slightly redesigned. The game will not longer play off melee hit and spell hit in the background, and instead hit will become a single stat that works on all classes. Expertise is also being altered to give a bonus to all classes, by negating dodge or spell miss, and then parry. Hunter ranged attacks can now be dodged, so they will be more balanced once the melee deadzone is removed.
Block is being moved to a separate combat roll that follows the first. The game will first roll to see if you parry or dodge, and if you fail to parry or dodge it will roll again to see if you block. If you fail both those rolls you will take the full strike. Be aware this is a slight nerf, since it means tanks can no longer "cap out" their block/parry/dodge to reach a near 100% chance of one of those items firing over taking a full strike.
Critical Strikes are being altered to baseline X2.0 for all classes. If you make a successful critical strike roll you will always do double the damage of the strike, rather then the current design in which many classes only did X1.5
Resilience is being abolished in favor of two new stats. PVP Defense and PVP Power. All characters will have a baseline 30% PVP Defense, meaning all players will have a natural damage reduction versus other players to make PVP battles less about burst damage. As one collects PVP gear this stat will increase, making them even more difficult to kill, while also giving PVP Power, which will increase damage versus other players, as a way to counteract other players PVP Defense. These stats are not included in the item budget, meaning they don't remove other PVE relevant stats like Haste. However, since they will not be budgeted into the scale, a PVP gear tier will be one tier lower in item level then PVE gear. Though that seems bad, due to PVP Defense and PVP Power, one in the higher item level PVE gear will likely not survive well in PVP situations, even though his item level is higher, because he does not have any stats to counteract the PVP players high PVP Defense.
Some interesting changes, and it will be interesting to see how they work out in the end.