Why do I have to KILL a merc for him to join me!?!?!??!???

I literally get 1 shot by all mercs T11+ and hate this stupid mechanic. I have a crap merc from T8 that is worthless DMG like my character. Horrible league mechanic

I've found with mine there seems to be a fine line between them one-shotting you and being fairly easy. Some of them are still a bit more dangerous, but it could be that you need just a bit more defense, or position in a way that they are a bit safe. I don't stand right next to them when the spawn. Not possible for all builds.

How big a difference does the level make? My current Merc that I use is level 78 and seems pretty decent. I'm wondering how much better 83 would be. Haven't read much about this. I think I have to exile the one ive got to get them again at higher level though? Is that correct or can it spawn again while i'm using it?

Some of them have this teleport thing on top of you and boom dead. I had hard time fighting them even on map 10... while other is easy on map 15-16.

It makes no sense. Isn't 15-16 suppose to be way harder. Now I didn't check the map modifiers. But it's about same every map.

Yeah I think the skill and items do make a noticeable difference, it is probably worth thinking about them until you are beating them consistently so you can adjust the way you do the fight, particularly if they have something good. I think I got reflect by molten shell at one point.

Having self cast guard skill and popping it before the fight might be a possible option if getting one shotted, since the fights are predictable and fairly quick.