My favorite MP to farm is MP7. It's fast kills, decent key and demonic essence drop % and I don't really have to pay much attention while the place is getting face rolled. With the build I've been using things simply die FAST.
I've been working on perfecting the build to be viable for MP10 as well. When I would switch to MP10, I found myself having to kite FAR too much, and I was dying a few times (partially due to my low amount of HP). Dying (ever) is inefficient and unacceptable, so I set out to find a solution. And I found one.
After much trial and error, I've come up with a few options that make this build MP10 ready. I was determined to make my build work, adding survivability, without losing too much damage. I wanted to be certain this build is MP10 worthy, so I made sure to test this on all Acts, multiple keys runs, Ubers, even candy land (with zero deaths). And I did it with my red gem in helm, therefore only having 40k HP. I didn't want to waste your time with something that is not tried and true. If you have more HP than I do (and you should) then it's even better.
Here we go...
Cluster Arrows Loaded for bear. Big booms, huge crits. This makes everything in front of you die fast. This is where the bulk of your DPS is going to come from. One awesome thing about Cluster arrows (besides the damage) is it doesn't get slowed by the slow bubble (Act 2 KW, or Zoltun Kulle). You click, and bam... Hits the target. I found this also better (than spike traps) against enemies that would jump around or teleport past your spike traps. With this, there is no escape. They just get jacked in the face.
Stun Grenades (This was the key component I was missing between MP7 and MP10). For MP7 or below, I use tinkerer for hatred regen (more Cluster Arrows). Stun grenades provides less hatred regen, which in turn would provide slightly less DPS, but the survivability increases dramatically Much needed for higher MP levels. You are taking FAR less damage with stun grenades. If you have a jack ton of HP and a lot of resist, you might not need stun grenades. Try back and forth between tinkerer and stun, to see which you like better. For Ubers do NOT use stun grenades. Make sure you switch to tinkerer.
Companion: Bat. Here you have an option. If you want more survivability, go with the boar. But I found my boar kept dying, fairly easily (especially on higher MP levels). So I decided to go with the invulnerable bat, for hatred regen and not worry about it.
Guardian Turret. You take less damage, and the small amount of DPS from the turrets help a little bit. When you do Ubers, you won't need this. Replace it with Marked for death (Mortal Enemy).
Gloom Do I really need to discuss this one? And as long as you are specced for nightstalker and have around 2+ APS with 40+ crit chance, you should be at perma gloom status. (even at 30 disc)
Prep-battle scars 99.999% of the time I never even need this. Gloom is always up, thanks to nightstalker procs. If I ever get REALLY low on health, one cluster shot with gloom on and I'm back to full health. But when I actually do need this... I NEED IT. It's just all around a good insurance policy to have, in case you screw up your rotation or overshoot your gloom (which can happen in cases like the Seige fight, if you aren't careful). It's also a great extra heal when things get rough.
Archery Bigger crits (or more crit chance, if you are using a 1 hander). More damage. Self explanatory. If you need more survivability, drop this for numbing traps. In fact, doing this will cause your DPS to go down a little bit, but your survivability will skyrocket. I prefer more damage, but when I use numbing traps, MP10 becomes borderline faceroll.
Nightstalker For permagloom. Disc regen is off the chain with this. It's the backbone of this DH tank build.
Grenadier This passive covers the two main attacks of this build (grenades and cluster arrows)... So it's just too juicy to pass up. +2 additional hatred per grenade -10 hatred cost for Cluster Arrow.
So if you feel froggy, give this one a shot. Works well for me, and it has for quite a while now (been using it [or a variation] since about paragon 35 - even when I had half the damage I have now). A few things that can make this build even juicier, is a Stone of Jordan with fire damage (again covers both grenades AND cluster), 30% elite damage, and grenade damage or -5 cluster cost. Also, a dead man's legacy with a -5 cluster cost (That's going to be one of my next upgrades)
Anyway, if you try it out, let me know what you think.
Good luck and have fun!
TLDNR: Cluster (loaded for bear), Stun (or tinkerer) Grenades, bat, guardian turret, gloom, battlescars, archery (or numbing traps), nightstalker, and grenadier. Worked great for MP7-10, it might work great for you.
Edit: One thing I forgot to add that helps tremendously with survivability while solo grinding... Give your Scoundrel a Windforce. Between your stuns and his knockback, you are taking very little damage.