I was killing bronze dragons with a polypore staff, arcane stream necklace, and a vecna skull. My magic level is 87, so my calculated hit was 385. I couldn't get my actual max hit, but I did hit as high as 401. As far as the other items I was wearing: full mystic robes, guthix cape (from mage arena in wilderness), anti-dragon shield, and ring of wealth.

I've hit a max of 446 on steal/iron drags, and i've hit in the 400s in barrows. I managed to get a screen shot of a 424.

 

 

It appears that the Vecna skull's bonus is twofold in this scenario.

 

- The polypore staff's base maximum hit is (magic_level * 5) - 180. The +6 boost to magic level provided by the skull thus increases the base maximum hit by +30.

- The +6 magic level boost also increases your maximum hit by +18%, in a similar fashion to other magic level boosting items.

 

The calculator appears to only apply the second bonus at the moment.

 

// We're attacking directly with the polypore staff. Discard everything we've done and recalculate. Maximum damage is (magic level * 5 - 180).
if(weapon_id == 10){
if(document.getElementById('polypore_staff_checkbox').checked){max_damage = magic_level * 5 - 180}
}

 

The above code is responsible for calculating the base damage. A quick and dirty solution would be to replace "magic_level" with "(magic_level + parseFloat(document.getElementById('potion_select').value) * 100 / 3)", such that the magic level boost is correctly factored in. I'm not sure if this double whammy occurs in other situations as well. If so, you'd probably be better off adjusting the values in the potion drop-down and then go from there.

 

That said, making this adjustment would lead to a maximum hit of ~430. I can't explain the 446.