Alright i'm gonna give you a couple of tips to make this easier for you guys hopefully:
1. Pray that RNGesus gives you a good sniper/revolver(makes bosses easier)
-Think i got lucky here since i got both but they were later in the game so i believe you can do it with others just max out dmg, reload speed, and clip size if you want. Also, try to save AP rounds for Tier 3 servers only trust me you'll need em.
2. Try to use explosive crates near enemies!
- They do alot of dmg especially against heavier units + you conserve more ammo and don't forget you can interact with them.
3. Abuse the revive system.
- Basically when you get to the hard data cap lvls the enemies can wreck you with some of the modifiers they have, so what i did was stealth around and run til i triggered extraction then i just get seen and die (OR try to get to extraction without dying). Then, you will get put right at the entrance it's pretty convenient!
4. Some general Boss/enemy stuff you should know if you already didn't.
- Emp Ammo disables cloak/titan aug making them vulnerable to dmg
- Some bosses can be attacked by others if they aggro them! But it's risky.
- In the kill X enemy lvls Abuse the alarms(trigger it then wait it out) to make easier enemies spawn unless you can kill bots and heavies efficiently.
Disclaimer: Be prepared to grind because this is gonna be fun! /Sarcasm