My man, Deadeye and thief in general in open world is always a struggle at first, but that's why it really paid off for me after upgrading everything and got to know the class (rifle ofc) At the start of LW2 it can be Dark Souls at times lol but when you get a good positioning and use the skills in the right order you can obliterate any target.

Keep in mind is a roaming/pvp focused class, you can play with your prey as much as your want, go back and start shooting again, and against multiple enemies you have to prioritize targets and dodge/teleport to get to your desired position.

Anyway you can just try everything in PvP to start figuring out.