Chargers are appearing in the wrong sorts of rooms, actually. They're not designed for open areas, but instead for complicated, maze-like rooms, and larger ones in general. If they just come at you in an open area, there's not a whole lot you can do. In a more complicated area, there's plenty you can do.
Many enemies actually have similar issues even if it's not super obvious. The problem is there's not enough categories of enemies for things to fit into and for the spawner to use. This is something I've discussed with Chris and he's said that just adding more categories would be easy enough.
However, these things are NOT meant to be easy foes. Some enemies are going to be genuinely very difficult. This particular enemy is designed to provide challenge via testing your reaction speed, and you're meant to use afterburners (or whatever it's called now) to keep ahead of them while firing at them.
That being said, I have already slowed the things down a bit for the next update. Along with fixing a few other issues with different enemies.
There's also the issue though that some rooms have enemy placements in general that are NOT where they should be; as in, jumpscare enemies being too close to doors (causing them to activate instantly). Or in a few specific instances enemies that are pretty much like 3 blocks away from a door you entered. This too will be addressed later, but it's not something I can fix myself.
This is likely to happen every now and then though. When it comes to shmups or similar things, I'm used to games that have a seriously absurd level of difficulty; this game at it's hardest so far is easy for me and this is likely to be the case even on high difficulties. As such I've a difficult time correctly judging just how tough something is until it's had enough time being tested by everyone else.
I probably will also gate the Chargers by floor number though, as now that I think about it that's probably a good idea.
For now though, many energy weapons or a simple barrage of missiles typically fries the things very quickly. They're too dumb to get out of the way.
Hm, come to think of it I may have also set their activation range too high as well. I'll check that.
As for the other things:
Energy weapons, yes, their balance is all over the place. Plenty of them wreck things too fast. That is to be addressed, but not by me.
The lengths of fights, this depends on what you're fighting. Right now, enemy HP is relatively appropriate based on their threat level. Boss HP being where it is is *entirely* intended. The nature of their patterns means that they need time to generate threat, and they also need to contain the player within them long enough to be able to do potential damage. Patterns like these dont work at all when they're not allowed to fire long enough. Basically every single boss would become pretty darn easy without these things.
There are actually very few games of this type that DONT do this. Even Binding of Isaac, many bosses have very high HP levels. The only reason why fights sometimes become short in that game is because of the potential for Isaac to become EXTREMELY overpowered due to the nature of synergies in that game. When a more normal run happens, bosses can take a long time to go down. The only exception I can think of in this genre is Nuclear Throne, where most bosses just dont have much HP at all. This also applies even to the basic shmup genre, traditional or bullet-hell. The length of fights in those is very close to what it is in this and bosses tend to not only have high HP, but multiple forms as well.
I havent seen any issues with it myself in this game. I usually forget the energy weapons are there and tend to just strike with the main gun, and it really doesnt take long to defeat most things. But you have to keep up a constant rate of fire actually hitting them.