You can't tell that from paper dps which you can find in your screen.
The legs/hour is mostly based on luck so I would recommend you to let the bot run about 2-3hours of t1 then save your exp/hour , gold/hour and then do the same 2-3h in t2. If your exp & gold / h are higher than with t1, go to t2. The same goes for moving on further.
There are also several things to increase your farm speed. Let your bot ignore trashpacks less than about 5 mobs so he dosent waste time killing every single zombie. If you see that you almost never die consider chaning some skills that improve your movement speed.
Most of the poeple recommend you not to leave t1 until you got over 1mio dps but thats bullshit. I went to t2 as soon as I noticed the gold and exp per hour was higher than in the previous torment difficulty.
You should never decide to increase or decrease cause you are having a low leg/h because it's luck based.