Just a quick dirty list of things I am probably going to tweak for the bosses in v5b.

Make Proto Man directly aim at you if he's charging a "juke" shot (where he throws his shield, but then aims at you instead).
 Add checkpoints for all shark phases.
 Add visuals to the invisible barriers in all shark phases (would the evil robot ones be fine here...? I felt it would look out of place)
 Make Shark phase 1 a little less tedious.
 Remove skyfloor push back in Shark boss phase 1.
 Changkey Dragon's bones to lose shootable flag when exposed.
 Nerf Shark phase 4 yellow beams to be less insane.
 Distribute Health pickups more evenly for fakeman chase.
 Make Bass's phase 2 easier (plenty of suggestions made for this but need to decide which ones to go for).
 Move the player spawn slightly forward in Quint's fight phase 4.

bass 2's moving background makes it easy to lose him. not sure how you'd go about fixing that, though.

i get that quint is supposed to be intentionally insane but having a full health refill between each phase and no respawn is a bit much. perhaps a bass-ish style healthbar, refilling between phases and stopping at lower and lower intervals until you finally kill him, with him actually stepping up his game between phases?

protoman feels too tanky for being protoman, but that might just be me sucking.

I personally think the difficulty of Bass 2 is just fine and that people need to git gud. He's not that hard.

However, Super Adaptor is a huge trap in that fight. The homing attack works fine against normal players because they move comparatively slow, but Bass spazzes around like a jackrabbit on so much cocaine which messes up the homing and makes it miss more often than not. I found that fight easier to do buster only as opposed to the intended way. If possible, the player should be given a special version of Super Adaptor that has much better homing for that fight only.

That can't be done, the moving buildings are done via a skybox and the skybox "moves with you" if you know what I mean.

Will add.

I still want him to be a challenge so instead I made him take more damage during the first phase to speed things up and get to the juicy stuff.

Been banging my head against Bass 2 for about 30-45 minutes and I don't think he's as badly designed as some people say... although that's not to say he's not a bad boss. For this I'm going to be rolling with the idea that Super adapter is a standard video game normal mode and Buster only is the hard mode. In such a situation normal mode can be brute forced to some extent and as such only a mild understanding of the boss is needed. For hard mode a better understanding of the boss and his abilities is needed (you'll get gunned down long before you can just outdps the boss), thus should be considered the "proper" difficulty as it is the one that good balancing of every mechanic is more vital to. Might have to do with the fact that I've only been doing buster only, but yeah...

Alright, so let's consider the fight at a first glance.

He's flying ALL over the place, I can hardly hit him! He's outmaneuvering me and is landing a lot of shots but I only have a limited amount of health to grab. He holds still- or at least, sort of- when using his special attacks, maybe I can use that. But all his special attacks tend to at least graze me too and I'm dead before he's at half health.

Considering Bass's character traits (hotheaded, wrathful, cocky, made as powerful as possible to kill Megaman) I've extrapolated the idea that he's meant to beat you when it comes to the neutral game- which is to say, when he's flying around taking potshots at you. On the other hand, as has been said before me:

The fact that he's most vulnerable during his power attacks fits his character; he gets cocky and thinks he's cool or some shit when he's actually about to take a few dozen shots to the dick.

It fits the concept of Bass to want to just end it with one huge attack or whatever to show his power when realistically he would win if he just kept his cool and shotgunned you down from afar. If I'm right, then the problem comes to light: the mechanics of the fight.

The Good:
The rapid fire purple shotgun special attack.
Holds him still for a couple seconds so you can take some shots at him and is relatively easy to dodge if you're on top of the situation (which as I've mentioned is your "advantage" over Bass). Feels like a quick rush of relief any time it comes up amidst a desperate situation.
The two-wave raining special attack.
A huge display of firepower that leaves him open for a relatively long amount of time is great and fits the theme of the fight to a T. My only complaint is that it's not actually as easy to dodge as it should be, considering the same theme of the fight. AFAIK the idea is to jump when it hits the ground, sidestep slightly, and jump again to avoid the explosion radius, but it's usually going to graze you. Make shadows on the ground to know if it's starting directly above you or not and maybe reduce the blast radius a bit?
Non-respawning health.
A bit of a surprise, but the fight should feel like he's the superior robot that can and will kill you if he doesn't get cocky. Having limited health puts your back against the wall, so to speak.
The Bad:
The freefall nature of the fight.
This causes a couple of issues:
1. Difficulty keeping your directions
When you can't tell exactly how fast you're falling or where the ground is, you lose your footing, can't dodge as effectively, and can't fire on Bass as effectively. Thus you tend to feel less in control (again, your "advantage" over Bass) of the arena.
2. Bass is kinda floaty?
When charging a special attack, Bass seems to float upwards a bit. This makes it somewhat harder to hit him despite the fact that it's meant to be your opening to attack him.
Bass's positioning.
I get that he's meant to outmaneuver you, but he loves to stick his face where he shouldn't. He loves to get point blank with you on a small island forcing you to move, but if he's just started a special attack you're probably gonna have to take the brunt of it as you need to make your way to the next island. I haven't personally had any issues with him running under the floor but I've seen it on streams.
The Ugly:
The triple shot and fist special attack.
Three quick ones that are more likely to connect than the purple shots are bad enough, but the fact that he has a homing shot goes entirely against what the fight's meant to be. I get that it's probably a lot easier to dodge with the super adapter and that you can dodge behind the pillars/platforms, but even so needing to maneuver like that both forfeits your chance to take advantage of his special attacks as well as automatically puts you on the defensive as you need to reorient/position yourself on the sketchy platforms.
The rising bullet hell special attack.
Considering the telegraphing it's not TOO hard to dodge, but you're probably gonna take one or two hits anyways, more if you're positioned poorly. Another attack that automatically forces you on the defensive, but this time he doesn't even leave an opening at all, he just flies back up. Make him float in place longer after the ability ends?

In summary, I feel what Lego(?) said sums it up best: Bass 1 was meant to feel like every shot you took was your fault, and it does. Meanwhile, if done right, Bass 2 should feel like every shot HE takes was HIS fault.

...Also, I beat him first try after writing this, so I'll take that as a sign that I'm on to something

P.S. Restore health before Wily Capsule, just a Q.O.L. thing.

speaking of Bass, a bug I noticed on his 1st form, he always seems to react in pain every time he fires a charged shot