The next big boss fight after Wallclimber had me hard stuck for about 7 hours until I eventually built a plasma monster, 2x plasma cannons, 2x plasma mortars on heavy legs. I was really sleeping on the AOE DOT damage, those plasma cannons are better than I gave them credit for. Great for clearing trash mobs too, one shot and you're done. They carried me well on my 8 or so runs farming Wallclimber to get enough cash to get all the heavy armor parts I wanted.
The boss in question had a pulse shield that was ruining my day and after countless attempts of taking down the shield with the pulse rifle or sword and then doing fuck all damage afterward, I decided to just run plasma and deal mediocre damage to the shield and decent damage to the healthbar. It worked out fine. Plasma isn't my first go to weapon to break pulse shields but it does the job well enough, better than bullets.
Tl;dr everyone try the plasma rifles if you haven't
I was already doing a plasma rifle, but the warnings about Balteus convinced me to do some tweaks to optimize the build before going into the End Of Chapter 1 mission. Inverse legs, lightweight arms, the starter head (it's better than the flat-head and it still fit, every other head either made overweight or over-energy). One plasma rifle, one sword, one plasma-mortar, the big volley-missile-mortar, and speed. I might not have been as tough as the full dual Meefcake, but I killed him with style, even finishing with the sword. I honestly couldn't tell if I died or he did in the final explosion, then the dust settled and I had one notch of health left.
Took about 2.5 hours of trying.
Holy shit that was fun. I've played Armored Core games, but only the early ones that didn't have Soulslike bosses like this. That was goddamned amazing.