According to Travis this is all going to change. Here's the full post:
"Rifts have always been intended to be the most efficient play method in the game, currently they aren’t for a number of reasons. Part of this has to do with the high level of efficiency in farming that players find doing things like farming Manglemaw, Razorclaw and any other number of unique monsters. Another contributing element is that farming chests without having to actually fight monsters is far more effective than actually fighting the monsters. It is very important to us that chests are exciting to find and feel rewarding but presently they are far too common and reliable to farm in certain areas of the game.
Finally Kadala, she has always been intended to give players some degree of control over their item upgrades. While we don’t want players to simply pick and choose from a list of items at an excessively high cost, we do want you to have an answer to the question “How do I upgrade my boots?” Kadala is meant to be that answer, she is meant to give you some direct control over the types of items you find. Since we are increasing the overall reward structure of the game she is also going to be increasing but by a larger amount than the rest of the changes since she didn't feel rewarding enough to us."
Bonus Legendary Drop rate for Rifts is also being increased from 25% to 100%. Which to be honest, is pretty freaking rad.