Helldivers 2

Armor is medium with crouch bonus.

If you're willing to spend SC on armor, try to get the FS-38 Eradicator armor from the rotating shop. To my knowledge it's the only light armor with the Fortified mod ("Further reduces recoil when crouching or prone by 30%. Provides 50% resistance to explosive damage."). I think that's the armor mod you're already running, just in light armor. I don't find 50 armor makes much difference, but the extra mobility really does. The recoil bonus is whatever, with that armor mod vs. bots the explosive resist is the real juice.

For clarity, the Fortified bonus to explosive resist doesn't require you to crouch or go prone to get its effect, you only need to crouch to get the recoil bonus. With Fortified you can sprint around and get hit by a rocket, or run over a bot mine, and not die if you've got full health. There's a separate bonus vs. explosive damage from crouching or going prone, but that's universal and not tied to any armor mod.

everyone is getting there faster and killing things faster because they got there earlier

Could be because they were wearing light armor. Armor seems to provide a really poor rate of return in this game, but light armor's bonuses to speed and stamina regen pay sizable dividends.

Adjudicator

My go-to primary vs. bots used to be the pre-nerf Slugger (RIP sweet prince), now it's the JAR-5 Dominator. In both cases it was because the weapon could handle Devastators. If I run out of AC ammo while facing down Heavy and/or Rocket Devastators, being able to switch to a primary that can stagger and kill one can save me. JAR-5 does take some getting used to though. It's 3rd-person handling is poor, but it's tolerable in 1st-person so that's generally what I use with that gun. The JAR-5 also has relatively slow bullet travel time that you have to account for. Now that I'm used to it though, I don't find any other primary as effective vs. bots.

mortar sentry

I've never found the mortar sentry all that effective vs. bots, they don't seem to clump up as much as bugs do. EMS Mortar can be a pretty good option for crowd control though. Personally I run laser (for major objectives or Eye of Sauron towers), Eagle Strike (for small bases and patrols) and Eagle 500 (mostly for tanks, walking factories; AC can take out tanks but oftem it's just quicker to 500 it).