I am somewhat ambivalent on the way they changed MF running. I loved clearing to Mephisto or Diablo (you know, the legitimate way), but it did get really tiresome after the 1000th run of doing pretty much the exact same thing against the exact same boss. I miss the whole crossing your fingers in hopes that something off of the boss' loot table would drop, but I kind of like the whole easter egg hunt way with the randomized elites that they've done it in this game.
I'm not sure if they changed it on PC as well, but the waller ability seems really dumb now. Maybe it's just the zommed-in-way-too-much-on-console perspective, but it seems like the waller types just got incredibly dumb with their AI. Not dumb in a broken way, dumb in a nonsensical way. They keep putting up walls that prevents them from attacking me as well as me attacking them. It's more annoying than difficult. The only time I've had that be an issue is when I ended up fighting an Arcane, Waller, Molten and they walled me inside of a box with two lasers dropped beside me with magma underneath.
There's very few instances where you actually need to lock onto a target. It's almost always in regards to the leader of an elite pack too. I don't really understand how the setup is ruining your hand either since all of your abilities are on the right, and lockon is on the left. You control your character with your thumb. I guess if you hold the controller with a vice grip, or have arthritis it could be an issue. I'm sympathetic when it comes to crummy control schemes that make you do finger acrobatics or cause too much strain, but I'm not finding this game to be one of those cases. My right hand hurts way more from playing on the PC with a mouse.