"Augment your ancient legendary" feature diminishes the gains from paragon since it raises the base amount of mainstats, therefore lowering the percentage of power gains from each paragon after 800.
this feature will also take a lot of time to "finish" on your char, because that's ~12 extra gems you have to levelup as high as possible and one extra gem per slot that you want to upgrade from a previous augmentation.
edit: also it only works with ancients, which makes ancients more important, giving players another reason to farm items and not just paragons.
this is a clever design where they didn't really change anything (you still get + mainstat), but shifted the game from paragon grind to gem grind, giving more of an incentive to farm as high as possible grifts, instead of "low" speedfarm grifts all day.
Ok, OP, it seems you've missed the point of Greater Rifts entirely.
They are meant to NOT be beat-able. They ARE the end game, which is why there is an 'infinite' amount of Greater Rifts.
Being able to perma-CC mobs completely side steps different mobs abilities. Coming soon, you'll HAVE to worry about winged assassins jumping to your DPS'ers, who will in turn have to start taking defensive skills / passives / runes. You'll now HAVE to worry about every mob type to varying degrees, which I personally think is very healthy for this game.
The fact that you're calling it 'dumb design' when different mobs types can cause huge problems for your group is very telling. I applaud Blizzard for fixing this issue, and I hope they keep up with it in the future.