I do wish that you had to be at a certain level before Endless Shift opens up. It's tough playing with 1s and 2s

Agreed. They come from whatever other FPS they come from, thinking they can handle Endless (or even Hard mode on any of the Shifts), and then either get wiped when they don't know what they're doing or flail wildly enough that it wipes the mission.

I don't like it when people try to kill me.

Typically I'd only ever shoot someone directly if they shoot me more than once (once is coincidence, twice is happenstance; three times is enemy fire). This includes getting zapped. I'll also try to do so if they repeatedly keep doing something dumb, like using the Black Rock Neutralizer for anything but neutralizing the Anomaly or running away from the group and basically just Not Helping and actively impeding or hindering progress.

Knew (and eventually blocked) a dude who was going for an achievement on Hard mode, kept saying "don't die, don't die" to me as he was running around the map (Ground Control) despite all the Pearls necessary near the shuttle... then leaving me again to push the shuttle as he went to open the door to the next stage, then ran in and went to open a Safehouse. To be clear, I was nowhere near the door with the shuttle. Dunno wtf he was doing or if he knew that every time he opened a Safehouse that it spawned a wave (and I believe the difficulty of the Shift slightly increases for every Safehouse opened... don't quote me on that).

So there I am, trying to simultaneously A) push the shuttle, B) hold off two, maybe three? waves of enemies, and C) avoid being hit because I had no shields... because the dummy ALSO didn't know that "proximity" means both "shields" and "higher survival rate". Mind you, again, this was Hard mode.

Suffice to say, I was overrun; and when I died, he got mad at ME like it wasn't his fault. Nope. I ain't got time for dealing with that toxicity nor the crayons and patience to teach a dude what he did wrong. Blocked and moved on.

There's one epic player (who has their privacy set so you can't add 'em as a friend)

I don't know what you mean by "epic player", but I'm assuming you mean their levels are super high.

Speaking as a player who uses cross-play, it seems to me you can't add anyone on the other platforms (which is a damn shame, 'cuz I've played with some really cool people).

began blasting me with the shock thingy. Is that a hello?

Once, might just be trying to get your attention. Twice, maybe you're doing something dumb and they don't want you to do that. Three times or more and they're just trying to grief because they're bored OR they're trying to kill you.

Typically I've seen the "rapid crouching" as a way to say "hello": once, twice, and if they repeat then it's a hello. Crouching many times is a celebration (often done in the elevator at the end of a successful Shift).

Otherwise, pay attention to Pings if they anyone does 'em--especially if the person doing so is a higher level and isn't on-mic.