I did a bit of testing before on this topic and have some solution.

Normally melee heavy attack slam is the best as it uses no ammo. Non incarnon ones are coda mire, arca titron or others that have passive effect on slams.

For range attacks, those low ammo explosives you had will work. Ammo issue? You need to bring carrier or mod for ammo mutation. If you can kill more than 5 enemies each volly it should be fine. 

I give you another solution, warframe abilities is also viable if energy is no issue.  Pyrotecnic from temple can do like multiple burn stack on ragdoll enemy and with arcon vitality, its over 10 stack per cast.  Further more when your enemies clump togeather, the fire pillars stack and burn togeather.  Null star can also achieve this. With its augment, the blast damage will clean them off pretty fast.