DiabloFans

FWIW, it was 100% reiterated and reconfirmed in a post today that the equation simply is 1.15^N:
http://us.battle.net/d3/en/forum/topic/12471197317?page=27#523

I still think it's misleading to compare the drop rates with MF inside of a rift against the drop rates on a higher torment outside of the rift. It's not a good 1:1 comparison.

Really what it comes down to is let's say you are farming T3 rifts with 0 MF. If you can farm the T3 rift with 150 MF, and your kill rate is less than 15% slower than with 0 MF, it is worth it to wear 150 MF. That's also the same rule to decide which torment level to play on. If you can do T3 and it's less than 15% slower than T2, then it's worth it to do T3.

It should, I think, assuming your MF chance is multiplied against the separate torment/rift modifier. 10% of 150% MF is 15% legendary MF, which is the same thing as the legendary chance increase going up one torment level.

This post is built on a completely incorrect assumption. It was confirmed by Lylirra in that very same thread that it is, in fact, a 15% multiplicative per torment level buff (eg 1.15^N):http://us.battle.net/d3/en/forum/topic/12413271220?page=13#241

Taking this into account, the drop chance for 150 MF is effectively the same thing as farming a rift one torment level higher. That is to say, farming a rift on T3 with 150 MF is effectively the same thing as farming a rift on T4 with 0 MF. It is nowhere near the drop chance of T6 rifts.

Very disappointed to see such clearly incorrect and misleading information be prominently displayed on the front page of the site.