Tips for Weapons Testing Site mission?

If you're still using a version that has a vertically-aligned door and pressure-plates, then just creep up to the point where the door opens without actually crossing it and use whatever long-range attacks you have available. When he goes to make a move at you, back away and the door closes, resetting the a.i.

On the other hand, if the entrance is a drop through a lunar base hatch, you need to invest 20 durasteel in a grappling hook and get your hands on a bouncy grenade launcher. Equip the grapple to one hand, the grenade launcher in the other and flip the switch. The default length of the grapple is just enough to drop you across the sensors (and hence open the door beneath you) without fully dropping into the room and activating the boss.

It's cheesing, but not cheating.

 

I actually tried that strategy myself, and it didn't work. Maybe it's just because I was using a plasma/electric grenade launcher, but they weren't
really doing any damage. Maybe it was patched or something?

 

That might be a possibility. I'll check it out sometime today and report back. I'm on the nightlies, so if it's been fixed I'll be effected.

Edit: Just checked and it still works for me. Perhaps you're damage is low enough that it's taking a minute to actually register on the enemy health bar? If armor values work like damage reduction, than you may not getting past it at all depending on how long ago you picked that grenade launcher up.

Mine's got regular bouncy grenades, I guess, but I don't think that that should have the kind of effect you are experiencing.

 

I recommend going in with a good food buff active. My personal favorite (for this fight at least) is Cyanider - the jump boost will help you dodge his dash attacks, the max health, while not the biggest boost, will still help you survive, and it's easy to make.

I will also recommend making the Glitch staff, because it's possible to absolutely wreck this guy's health bar if you time the activation right. You should have juuuust enough time at the end of his Overload attack to find a safe spot, charge it up, and drop the rift right where he lands for, as the classic meme goes, Massive Damage.

Overload and the Missile Barrage also become easier to deal with if you practice your perfect blocks with your shields/two-handed swords.