Am I doing something wrong?

I've been playing this game for about 15 hours. After getting my character and weapons to level 50, I started farming wedges and upgrading everything. Once I got all the gear I wanted and thought was the best, I expected to kill enemies much more easily — but I was kind of disappointed.
Even now, it takes me about a minute of meleeing or several full magazines just to kill a single Primander. In defense missions, this makes everything take way too long.
Am I modding my gear wrong, or is the game just supposed to be like this?

https://preview.redd.it/pz7hxhswapyf1.png?width=1913&format=png&auto=webp&s=fbaeb1715d771282a8b8d36b9b6d62b3dad70413