Hi there!
After some in-depth testing, I have discovered the following inconsistency which I believe to be a bug:
If your infernal blow charged debuff expires on an enemy, exploding, and you hit that enemy too quickly after the explosion and then keep hitting it, it will not explode again.
To elaborate here are several step-by-step scenarios, I have replicated each many times over the last hour of testing:
Control Scenario:
1. Hit enemy with infernal blow
2. Wait for charged debuff to expire, exploding
3. Hit again after a small delay
4. Wait again for charged debuff to expire
5. Enemy explodes again
Scenario 1:
1. Hit enemy with infernal blow
2. Wait for charged debuff to expire, exploding
3. Hit immediately as charged debuff explodes
4. Wait again for charged debuff to expire
5. Nothing happens, no explosion
Scenario 2:
1. Hit enemy with infernal blow
2. Wait for charged debuff to expire, exploding
3. Hit immediately as charged debuff explodes
4. Keep hitting without any gaps longer than the charged debuff duration
5. Enemy dies without exploding
Scenario 3:
1. Hit enemy with infernal blow
2. Wait for charged debuff to expire, exploding
3. Hit immediately as charged debuff explodes
4. Wait again for charged debuff to expire (i.e wait at least the length of the debuff duration)
5. Nothing happens, no explosion
6. Hit enemy with infernal blow again
7. Enemy once again gets debuffed and explodes (either when you kill it or
when the charged debuff expires)
From this testing, it seems that if you hit too soon, as the debuff is expiring, it applies a 'ghost' charged debuff which refreshes with each new infernal blow hit within the normal duration of the charged debuff. This 'ghost' stops an actual charged debuff from applying so the enemy won't explode unless you let the 'ghost' debuff expire and start again.