Okay, let me explain my observations in detail. Unless I’ve got a different game than everyone else (which I doubt), this is what I found how it works. I’ve spent a lot of time keeping statistics and calculating and testing (I’m a Wiki contributor) to figure out the exact formulae for melee and Blitz at any level and then spent a lot of time testing if they accurately predict what’s happening in the game. I wouldn’t be so confident if it didn’t.
Note: Mayhem bonuses do all sorts of funny things to this which I haven’t really looked into yet. But when there’s no mayhem bonus that applies here (like melee or skill damage bonuses) it’s the same as in non-mayhem, just tested it and it works–specifically, Blitz’s +100% melee damage still works when it’s on cooldown. So…
This particular test is in TVHM without any enhancing gear or skills other than Blitz to keep it simple. I’ve tested my formulae with more complex setups and it’s always worked so far. Sadly I’ve got +2.8% melee damage from Guardian Ranks because I didn’t think about it first, soon realising that it’s a complete waste to spend them on melee. But incorporating them here should show if the formulae are correct.
Base melee damage is 18 * 1.09^level, that’s 1338 on level 50.
Total melee damage is BaseMeleeDMG * (100% + additive bonuses) * multiplicative bonuses.
Blitz does three things:
+100% damage (you say only when procced, I say always)
Multiplicative (only when procced):
A) converts damage to element, I’m using shock against skags in TVHM here, that’s *0.65
B) additional multiplicative damage bonus (not mentioned in game): *(75% + 1.5% * level)
A) Without any melee enhancing skill:
18 * 1.09^50 * (100% + 2.8%) = 1375.9
If Blitz doesn’t do +100% on cooldown as you said, it should be the same value in that situation.
B) With Blitz unlocked but on cooldown according to my logic:
18 * 1.09^50 * (100% + 100% + 2.8%) = 2714.3
C) With Blitz procced:
18 * 1.09^50 * (100% + 100% + 2.8%) * 0.65 * (75% + 1.5% * 50) = 2646.49
Test results in game:
No Blitz unlocked: 1376
Blitz unlocked but on cooldown: 2714
Blitz procced: 2646