Solo is definitely tough. The enemies rush effectively and use cover well. I would suggest you use you next skill unlock on the drone that heals you. As soon as you start a battle pop it off and that thing makes it very difficult to die. It lasts a long time. The other skill I would recommend the oxidizer chem launcher. Quick cooldown and it does solid damage/CC. You could always use the revive hive too because you can revive yourself with it if you’re playing solo which is very useful.
Basically I think solo is tough but possible. Use the skills often and I think you’ll be alright.
I unlocked that drone first chance I could. I do forget to pop it sometimes though. I have the turret as well but I always throw it too soon. If the rushers were toned down just a touch this difficulty would be perfect not easy by any means but when 2+ rushers come it’s basically game over for me they are so strong.