The spread patten is the price you have to pay for the power and 'always hit' feature.
Slugs *won't* always hit, so that's not a factor, and the slow reload and one-target boundries will likely keep it from becoming over-powered.
I think shotty and chaingun/pistol balance each other out and with weapon mods coming in the next version the weapon landscape is bound to change anyway.
Speaking of mods, maybe a shotgun specific mod...
Well, I don't know anything about weapon mods just yet, so that may change my POV, but for the time being, I'm thinking aloud.
As for chaingun balance, I don't know... From my recent SG-training experiences, it seems to me much easier to play through a game not using SGs than it is to play not using CGs. Even trait-wise, EE's needed to keep your RLs working smoothly (and that CG), but Reloader's not nearly as so. EE will still be needed to work AssltSGs well, but at least you won't need ~3 10mm spaces and a CG to back them, too.
Since Doom had a tighter spread patterns, why not tweak the Combat Shotgun (or the Shotgun, or both) so it has a spread pattern more similar to the original? I think it could do the trick, too.
Aye, possible - making CmbtSGs narrow-angled, permanently or switchable w/'R' (the current 'R' doesn't seem to coserve reload time anyway, so it's better to control-'r'eload, one at a time).
But narrow-angled shotguns still don't fulfill what I had in mind, because they'll still lose a lot of power at medium range.
As for the quick-slots, maybe they could be tweaked? I was thinking, if 3 would choose the best (arbitrary) SG, you could still 'i' pick a "lesser" weapon, and the UI can include defining keys to weapons (restricted to keep it DooMish :P ).
After all, DblSGs out-class shotguns in all ways, when they can 'R'eload one barrel, and in most ways seem to out-class CmbtSGs by firing*2 where CmbtSGs fire->pump->almost fire ( and that's assuming they have shells left in them).
So, IMO:
1- LS, Combat Knife
2- (Plasma Pistol?), Pistol
3- Double Shotgun, (Assault Shotgun?), Combat Shotgun, Shotgun
4- Chaingun
5- Rocket Launcher
6- Plasma Rifle
7- BFG9000
8- Chainsaw
Special weapons will out-rank their normal class and then be picked by a first-inv-slot basis, possibly unless otherwise keyed by the user (who can, BTW, key them only through 'i'nventory ('K'?) to avoid lists that may spoil, although keying will then be permanent 'till changed again).