... per Frenzy Charge

I see the 4% run speed per Frenzy Charge is additive, so 4*6=+24% run speed
The 6% damage per Frenzy looks correct at 12% per Charge... haven't checked its math out yet
And I see the 2% attack speed per Frenzy Charge is not, I've got both 2%'s and it only changes it to 9% per charge over the default 8%

if it was 2%*6=12% increase to 8% base frenzy speed so 8.96 or 9% but I have two of these passives so it should be a 24% increase to the 8% base which is 9.92 or 10%.. or should it be additive like the run speed and increase it to 24% instead of 9%.

just what is the math behind the attack speed per frenzy charge?

no the base value is 5%...perhaps u mixed it up and look up the 8% from the frenzy-gem...but u made a screenshot for the normal atk, ofc the frenzy bonus doesnt get added there

Pretty sure the base frenzy bonus used to be 8%, but was nerfed to 5% per charge in 0.9.5.
Ironically, this hardly affected frenzy builds at all.. but was a serious nerf to conduit, which very few people even used before the nerf.

ah that explains why cast speed is only 5%! Thanks, I didn't notice that in the patch notes, started playing again in 0.9.5c

Mechanics post on Charges still list it as 8% per, last edited Dec 22.