Pragmatism would suggest that some is almost always better than none.
I would presume a human sized bug would be especially concerned about a cracked carapace, rather than cuts and bruises. This suggests bugs would not be too concerned about cutting and slashing weapons, but quite concerned about blunt and stabbing ones.
Blunt weapons deliver a heavy payload. They depend on sheer, brutish power to pummel targets into mush. It's clear to me that a typical bug soldier could suffer only minor cracks before secondary blows are lethal, therefore, armor that can absorb blunt attacks is desirable.
Piercing/stabbing weapons deliver the entire force of a blow into a minuscule point, the tip. This kind of energy concentration cannot be absorbed, but must be glanced or caught. It's clear to me again that well-placed stabs with enough energy can easily pierce the carapace (and potentially crack it depending on location and combined motions like twisting), therefore a chainmail would be desirable. Chainmail actually works on a catching principal, allowing a non-lethal length of the weapon's tip to penetrate the armor, but then catches the weapon where the force is weaker and spreads the energy out so that it can dissipate broadly.
To fit snugly over the rigid bug form, they should wear padded clothing first, chainmail over the joints and high movement areas, and a broad and sturdy breastplate over it all, with perhaps gauntlets and helmets, etc. Oddly, that's very similar to humans.