The Warden DEFINITELY shouldnt be taking 20-30 minutes to take down. I just... what. Even on terrible runs, I've never seen it go even remotely close to that.
Is this with Redshift? What happens with other mechs? Note that the game is very much not balanced with Redshift in mind; it's ability warps the difficulty quite a bit, which is part of the point.
I usually don't make it that far with other mechs unless I'm cheating, tbh, heh. When it does happen without that, though, it tends to happen because I got some serious firepower in one way or another and stuff dies fast enough it can't kill me, ehehe. Either by just dying in the case of something like the loco -- I three shot a first floor one of those with a starting/no damage perk precision railgun sometime today, iirc... the things are weirdly flimsy, and probably the easiest miniboss in the game for me just because of how little it takes to kill one -- or not being able to keep the screen saturated with bullets longer than I can avoid screwing up too much, which is the case with most of the bosses.
So with other stuff, if I make it to warden or beyond it either dies a lot faster or it kills me long before that sort of time elapses. With redshift, I can get a lot further with a lot
less just because it's orders of magnitude easier for me to avoid bullets with redshift. So item/perk combos that would have died floors earlier for me if I was using one of the other ones get to the 5+ range and just... start tickling half the enemies instead of hurting them.
Also, what sorts of items and weapons are you using? Are you hitting the boss (or other targets) CONSTANTLY with your basic gun, regardless of your movement?
As much as I possibly can, and I've been trying to poke at the game to see if I can set up the controls so it's easier for me to do it even more. There's occasional downtime when I'm concentrating enough on nudging around bullets I forget to stutter the mouse at the same time (this is marginally less of an issue now that I've noticed I can attach movement buttons to the main gun, but I can only seem to overlap two instead of all of them, so...), but usually I'm unloading the main gun on whatever I'm trying to kill as much as I can manage, which is most of the time when I'm redshift, at least so far as actual things-are-moving time. Items and weapons wise... that particular run, iirc I think
I had the turbo blaster, if I'm remembering the name right, as a main gun. The really rapid fire triangle/arrowhead bullet one, that's oh so sexy for something so mediocre in practical effect. It was either that or a fair amount of fire rate boosts and having been utterly shafted by main gun pickups (either due to not having the dosh to get them when they did show up or them just not really showing up... can't remember which exactly it was) and still toting the low-range minigun. Don't quite recall what the energy weapon was... want to say it was either the plasma shotgun (iirc, the blue one that slows/stops stuff) or I was still stuck with the precision railgun. Either way I do remember having something like... eight, nine shots worth of energy? I think along those lines.
The damage in general was just kind of garbage that run. Tremendous garbage. Almost certain I didn't have a net penalty, but it couldn't have been more than like... maybe 20, 30% total boost, if that.
As for using energy weapons, yes. Particularly on redshift, since it's (much) easier to safely/effectively aim and takes far less frantic multitasking, but just in general I don't tend to end a room, any room, and especially
boss/miniboss fights with any energy left, ever, unless everything died before I ran out of shots. So long as it's not something like a gravity cannon or somethin'. Bit more conservative with stuff that can kill me, ha.
So far as other stuff, consumables, robots... I try to use the former, but my general experience is the ones that are useful outside the boss rooms get picked up and I leave behind/forget the ones that are, and the offensive ones that aren't just stat boosts tend to be kinda' underwhelming. Nice enough but very easy to not prioritize and forget it was laying on the floor somewhere when it was time to fight the boss. Robots I get whenever I got the cash, heh. Definitely prefer the defensive ones but I'll take what I can get so long as it's an orbital instead of one of the other ones. Pretty sure that redshift run had both the plasma defense and the interceptor -- I distinctly remember the latter blowing me up a bit in one room because it kept insisting on shooting down those explosive floating mines... that were right beside me, heh -- and I think
one of the shoot-where/when-you-shoot orbitals, though I obviously forget which one.
Now, that being said, some enemies and such are very specifically meant to be quite tanky.
I'm much more okay with bosses/minibosses being notably hard to bring down, heh. It's just when a single regular enemy in a later game floor is taking as long (or longer) to kill as some/most of the early floor bosses that things start feeling kinda'... off. Moreso when it's got a twin and two friends that are only flimsier by a degree or two in the room with it, ehehe.
... anyway, hope that sheds some light on things. If not, I can try to clarify or... somethin'. Maybe try a run where I intentionally avoid damage boosts entirely, I'unno.