After completing all the main missions and strongholds,you're poped to "tier 1" i believe? (when everything turns red and black tusk takes over).
Anyway, some of the bounties are impossible. Me and one other guy tried to complete some of them - few were successful,few - not a chance.
I could waste 2000 bullets (of 300 gear score weapons), and do minimal damage to the boss,while he/she just throws one grenade our way or does one shot and we're dead immediately. Oh, and there are always enemies spawning all around you,so you have nowhere to go for cover,since they're shooting at you from all around you.
Makes people to avoid any kind of bounty hunting.
When you look at the details of the bounty it will show you what level bounty it is..
I don't know if they have challenge or not on tier 1 since tier 1 went by so fast..But you may be doing higher level bounties at times.
If you feel like they are closing in too tight on you,back up and try to keep them in front of you,if you can..Some places you are in a room..just back out of the room and let them come to you and just pick them off as they come through the door..
They may take their time sometimes,but they'll eventually come after you.. If they don't,then draw them there..
I learned this the hard way also when doing Hyenas..Never take cover where there is a sewer lid behind you.. that's where they come out of..lol
After you play everything before Tier 1, you get accustomed to how the game behaves. That goes out the window now. Initially, when starting a new tier, your armor and weapons might be under-powered. Every scratch feels like a knockout punch. You have to gradually improve your gear before taking on the more challenging bounties.