Why did you make non-Dualgunner pistol-only builds impossible, dev team?
Funny,
it doesn't LOOK impossible. Even if this is one of our best players, he still pulled it off on N! without a Trigun until floor 18. I think you might be a victim of some flawed assumptions. For example:
...In the new version, however, [playing an MSs build] makes me severely underleveled because I don't dare attempt the Arena with only one pistol and the Chained Court is worthless without the Arena completion, because the mods are inaccessible....
Hell's Arena has gotten a good deal harder with new AI, but imps, demons, and cacodemons haven't had a rewrite since 0994 (leaving only third-wave HKs and Barons to be the new challenge). And, correct me if I'm wrong, but I have always found SoG(3) to be superior to SoG(2) + DG as a matter of building your traits up. (I've written at length why this is the case, although the post would be pretty old by now: in short, SoG(3) gives you slightly more DPS; it allows you almost the same firing speed as firing two shots with Dualgunner, but grants you the chance to react in between; and you can swap for a pistol from the prepared slot instead of having to reload every six shots, giving you even more extra time.) So really, there should be no problem attempting Hell's Arena with a single pistol.
Even if you don't feel up to snuff on that special level, Chained Court is by no means worthless due to the unavailability of the mods: there's still a pretty good amount of experience waiting to be plundered (and, if I'm not mistaken, the problem you're expressing is related to lack of experience). On HNTR it's not a lot, but it's certainly free (that is, gained with no loss of health/supplies) given the amount of ammo and zerk lying around, and getting the cacodemons to come out is simply a matter of shooting down the doors. On HMP/UV it's even better experience and killing the HKs/Barons is actually exploitable right now, so it's still basically free.
I guess I'm not so sure what the problem is. Sharpshooter is meant to be a difficult build because of the lack of Dualgunner, but I wouldn't consider it particularly inferior. Personally I don't know if Bruisers are too difficult with clvl5 pistol builds, so this will be something to look into. I'd say you're definitely right about the challenge rating on the select screen: Marksmanship has, in general, become harder (especially with lost soul and revenant resistances), so it's a good idea to bump up the suggested difficulty.