I can see how it'd be frustrating, but if you stick with it you're going to get through any part you get stuck on eventually. Keep moving, dodge frequently, and stick a BMG as your second weapon so you can switch to it and recharge your shields with it when they drop. If you get hit hard, charge yourself up with the BMG while you run for cover, and then come back out and work on reducing their numbers and the amount of fire you take even if you do wind up dying. Don't forget your grenades, use them every chance you get.
The controller suggestion isn't a bad one, either. I prefer keyboard and mouse, but you're going to be better with whichever you feel more comfortable with.
If you really hit a wall, take a break and come back to it later. Sometimes doing that is enough to make you wonder why it was hard in the first place.
Here's what you do. Make sure you have a Respark or Hurricane Shield. They have less Energy, but recharge faster. You can shoot hide shoot hide.
Now, stay behind the crates and take out the first wave of baddies.
Rose will get cutscene and a little imp fire guy will run under Jackleg Joe and knock his shields down.
Now, blast him.
His shield will go up.
Fight off the waves some more, still staying behind the crate.
A burner guy will appear. Let him run to you, Melee him, when he's on the ground, shoot the tank on his back.
He's run away screaming, "It burnnnnssss" and run back under Jackleg Joe knocking his shields down.
Keep doing this, until you get a mini-scene, Jackleg Joe will jump down. Now just circle strafe him and unload what you have in him.
I used my FRC SAW, but whatever your high DPS weapon is, you can use that too. Once he's down, he's easy sauce.
He's just like the grednadier guys, Blacklungs.
If you still need help.
Just keep trying, you will learn. It really isn't that hard.
Take off auto aim. Usually this hurts you in most games because the aim is usually centered on target, you want headshots.
Learn keyboard mouse not gamepad, mouse offers WAY more precision and faster response. Learn it and love it.
Roll is your friend, when you see a rocket or grenade, ROLL! soon it becomes auto reaction just as running away is your normal reaction.
If you have the cloak ability, use it. If you don't and your new to FPS get it. It is the biggest life saving skill there is I think followed maybe by decoy. Just remember to run away from your starting position, they continue to fire and lob grenades at the spot they lost you at.
Try the different weapons, I leveled up my assault weapons to 10 before I realized I like the Light Machine guns. Scoped at 400 damage a shot with an 85 starting clip is nasty to everything. Burst fire to control that recoil.
Remember that if your weapon levels you will no longer gain experience in that weapon type if you continue to use it, so always switch out to a new one when it levels. Keep an eye out for backups to what you are using and don't accidently scrap/sell them.
It can get ridiculously expensive to remove mods from weapons. But recovering them becomes a priority when they are all level 3 mods... I sometimes use an unmodded or level 1 mod weapon to level till I have enough to recover the good mods, never scrap a weapon with good mods.
Use cover, before starting a fight make sure you have a place to hide behind to minimize the amount of guys shooting at you.
Roll, Roll, Roll... it is your best friend in this game when your getting your *** shot up.
Your Challenger won't drive? You're probably in the passenger seat.
Can't sell/delete an item? Check all of your loadouts, it's likely still equipped.
Auction house? Why? It'll just render bits purchased lock boxes pointless, and weapons are mostly equal anyway.
Gear/enemy progression? No thanks, it'll only render 90% of the content trivial when you reach the highest zone.
Also, I just did the Jackleg Joe encounter. Easy. As. Hell.
Eh. Not too easy if you're not quite sure what to do. I got frustrated my first couple of times, due to being sent back to the beginning.
1) Do all the sidequests, that will give you gear and help you gain points to put towards the EGO Grid which is effectively a leveling system.
2) Participate in as many Arkfalls as you can. You will gain lots of weapon XP from them, and usually a decent amount of EGO Rating at first. Side quests also help with EGO Rating.
3) Do Co-Op dungeons, lots of them. Just like other MMO's even if you suck and your gear sucks you can be carried as a dps through any instance. Chances are your group is decent and can clear the level without you. The good thing is you'll be able to practice your moves and not always be the main target of the enemy. Plus if you die your team will rez you.
4) Lastly increase your EGO Rating. Doing so will unlock more Perk slots. Which helps you also do a ton more dps.
For maximum damage I would focus on the EGO Power: Overcharge.
Overcharge + Perks
Risk Taker: When shield break your EGO Power extends duration by 15%
Killing Machine: Increases Overcharge Duration by 6 sec
Bloodlust: Damage recharges your EGO Power by 3%
Quick Charge: Reduce the CoolDown of Overcharge by 9 sec
Killing Spree: Increases duration of EGO by 6% on kill
Overcharge increases duration 60% (10s + 6s = 16s)
EGO Return on Shield Break, return 2.4s (15% of 16s = 2.4s)
EGO Return 3% per hit which is 1/2s (3% of 16s = 0.48)
Reduced CD by 22.5% (9s / 40 s = 0.225)
EGO Return 1s per kill (6% of 16s = 0.96s)
These will extend the duration of your EGO Power while minimizing the Cooldown.
I top dps charts with this build and if you get the hang of it you will too.