If you go with the Burning Nightmare mod on the EPC, then you can shoot your sludge puddles and light them on fire for additional Damage Over Time. This kind of works like the Combustive Goo overclock but with better crowd control and consistent DPS on many more targets. You can even go with the Neurotoxin Canister if you want more DoT, but it's better in Multiplayer in the case you have teammates with better single target damage.
This actually is quite close to the meta for sludge comp. The only major upgrade differences are stun on C4, Healthy and Breathing Room on Armor, and damage on pickaxe.
Also PSA: TCF doesn't interact with the EPC's stat block, meaning T4A, T1C, T4C, and the Overcharger OC all do nothing, and Persistent Plasma has no downsides.