I'm a little late to the game here, but I've been looking through a lot of the nuts and bolts of the base classes presented in the Beta, and in particular some of their apex abilities. And I noticed that the DC on the Ranger's Master Hunter ability doesn't scale up. And this is while the DCs on some of the other classes do. So, to preserve the current DC at level 20, and to allow it to scale up when epic, I suggest this minor change:
"The DC of this save is equal to 10 + 1/2 the ranger's level + the ranger’s Wisdom modifier."