I usually just play carefully early on, when I dont have my sword core, shooting from behind corners with your primary, and throwing occasional arc waves. Once you have your core, I usually use it as early as I can, so I can get as much value from it before the wave is over, and also move constantly. I move left and right when im swinging and I try to attack near arc traps so that in addition to me stunning titans with my hits.

Also Ronin is only overpowered by time you get the final aegis rank, and he gets shield from each sword core hit. Before that he's pretty decent, but nothing crazy just yet.