proximal tangibility? just how close am i supposed to get?

Comments
how close
Short answer: Yes.
Longer answer: Distance is extremely inconsistent by mob type and not necessarily mob size. Some huge mobs you need to share pixels with to hit while other smaller ones have much bigger distance to their proximal bullshit.
boom goes the grenades
Probably a bug, might want to file a bug report.
You know when you're at the ticket machine late at night for the local public transport system and there's a drunk guy who really won't stop talking to you, in spite you showing no interest or even replying to what he says? Yeah, so that's a little bit too far away, you need to get closer than that. Preferable distance would be where you are no longer able to lick the monster's ear on account of that you can't really open your mouth because your nose would get stuck on their cheek bone!
It's a real problem with some of the larger enemies. Those cleansed giant worm things are basically unkillable with proxy tangy, as well.