What MP do you bot on? I have a moderately geared barb and I do MP1 botting with no chance of dying no matter what happens. I've literally seen him WW in a pack of mobs sitting on top of plague, arcane, and molten, and just kill everything while sustaining his HP. I only have 3% life steal, 610 Life per Second, and 313 Life per Hit. I do see my Life per Second spike to ~8K and sometimes ~15K, but I suspect that's health globes along with the 5 piece Immortal King's bonus (5 Life per Fury Spent). Being WW/Rend spec (which is what I'm running on mine), you can fury dump (which the bot does nicely). I can do MP10 (though I kill things slowly), but my bot can't quite handle it due to it just tanking stuff a lot. I feel like it could bot on MP5-6 and only die to a few affixes, which is more than I can say for my cm wizard, who has more HP, higher resistances, and dies on like MP2, lmao.
Here's a good read on maximizing your IPH:
Which monster power level to farm? | Speed is king
I suspect there's probably a way for DemonBuddy developers to put some sort of downtime calculation into the GUI. It would be nice to have some sort of API that would allow profiles (or maybe some sort of plugin or even DB itself) modify the MP level based on deaths per hour or % of downtime.
Honestly, though, I would say botting on MP1 or MP2 will be the most effective if your gear is subpar to even mediocre to somewhat decent, just because the speed at which you will clear things will be so much faster that your bot will spend more time fighting mobs, getting less IPH in the long run. So, if you're on MP10 because you have a chance to get more legendary drops or better rolls, realize that the rolls aren't THAT much better, and that, though you may be eligible for more legendary drops in theory, you're killing a lot slower, and therefore getting less items per hour. You also need to factor in that deaths severely cut into your IPH potential. Dying is so much more terrible when you're botting than if you're playing yourself, IMO. Bot is all about efficiency, and I've seen Trinity restart an entire profile because of a death, which was terrible as far as time is concerned.
Give it a shot on MP1. Let it run for a couple of hours. Then swap to what you had been botting on and let that run for a couple of hours. Then compare numbers. I think you'll see that botting on MP1 is actually going to be the best bet for you.