My barb on non-season I have a build a WW build that allows me to move at 250% move speed. Which allows me to clear a rift on average in 2 minutes. I know wizards could keep up with me and monks. Demon hunters seem to be able to now as well.
Sadly this season I'm playing leapquake. And I move at a snails pace lol it's incredibly frustrating. And it's hard to tell if leap actually goes faster than 25% move speed and add to the fact that leap is frustrating to use as a moving tool considering half the time I just leap into the same spot. The clipping in this game is a bit annoying. Sorry my barb shouting and grunting all the freaking time is more annoying.
edit: to answer the question speed rifting is well down to how fast you move. Unless you can't 1-2 shot mobs. In that case simply ask yourself if doing a rift on T8 in 2 minutes compared to T10 in 5 minutes. With leg drop rate being 295% and 461% so not even double the drop rate. Yet it takes more than double the time.