I levelled a lot of gems and farmed a lot of gr keys with this build in the past and in 2.6.1 it became so much stronger!. Very fast in solo and group. Keep in mind it's a SPEEDFARMING build and not a GR push build, so they key is to kill everything fast and move as fast as possible.
If you can't kill everything in 1-2 blow because of low paragon/low damage/etc then just lower the difficulty. Not need to frustrate yourself and crawl through high tier content slowly. I do T13 in about 2,5-3,5 minutes at p1500 and no augments and 1,8 mill damage. What i like about monk in general is that he's very flexible with skills. You can stack a tonn of damage or you can stack a lot of toughness, or a mix of both. I will describe a few options and combinations of skills.