Sorry, I thought this was obvious for any player that plays efficiently. You need a pool every rift or so when you do rat runs. Hence the 2mins/1min value.
And 3 pools at 1 min per pool is 3 mins, which means you need to run a rift in 6 minutes for every 3 pools. This is slightly faster than realistic, but a good group can definitely go down to 8min average. 8min/3min is pretty much 1/4 of the time spent looking for pools, at paragon 3.5k. Which is not what an average player is, according to these forums at least.
Just because you do it before running the rifts doesn’t mean it takes less of your total play time. It means you do it at a point that is more convenient.