Crits are terrible for tournament play imo for reasons you're clearly aware of, but if it's not a serious comp and people dig them, that's cool...I can understand why people find them fun. Using them to make the game go faster isn't a very good reason to enable them though, as skill gap games will roll quickly anyway and close games will just be less close since they can be won over a lucky crit instead of a smart play.
There is really no positive or interesting aspect to damage spread at all though. For those unaware, damage spread just means the same shot done at the same range with the same aim falls into a random range of damage instead of a specific amount (note: not to be confused with splash damage from rockets, stickies etc. which is integral to the game and not something you can turn off). Disabling it just makes the damage from something at a certain range constant when it's not a crit.
For example, with damage spread on, your full scattergun meatshot might do less damage than a half-hit half-miss shot another scout hits you with for no particular reason other than pure RNG luck for him, even though neither of you crit. It won't help the game run faster either since it can do less damage just as easily as more damage - it's actually mostly frustrating because some shots you'd expect to kill won't because you got a bad dice roll.
Dustbowl is fair of course, in fact perfectly so if you're scoring it correctly since both teams have the same opportunity. It's been dropped in competitive because most people just don't like it.

If people at respawn do like it, there's no reason not to run it. It can be pretty anti-climactic though, so I would suggest you run it in an earlier round if you do.