I'm not sure if this is the same issue you are talking about here and I seem to recall something similar happening on the original game but I can't be 100% about that now as it was a long time ago.
My Commando can do a /flameSingle2 against a mob and all that happens is they die and fall over, I get no animation and no weapons sounds, in fact I don't move at all. I'm am guessing its because the damage done is much higher than the mobs HAM and therefore they die instantly but it would be nice to see the animation fire every time it’s a valid hit. It is easy to recreate as I just have to find a low level mob and call /flameSingle2, it does it on the cone command too if all the mobs are lower level than the damage dealt.