There is nothing wrong on it, I have Vanberk Snake head in idRO and it's actually good when you can roll dice for double attack and crit separately. People mistaken when stacking crit and DA is bad idea but when you see 4 hits DA, 5 hits crit, and 1 normal damage of 10 hits you will tell differ. The idea is eliminate 100% damage because you roll dice for either DA or crit (200% and 140%), imagine that you roll dice and number 1 is fail while 2-5 success (2-5 are DA and crit number) the chance for getting 1 is small..
Just because you have a vanberk snake head on idRO doesn't mean that it's great gear.
I mean, it's not a terrible choice (particularly with snake hats at 30m), but it's not really that good.
First, because DA takes priority over crit, when it's 100% crit procs, your damage increases from 150% to 170% (a ~13% increase in DPS) - vs a non-snake-head proc of vanberk (starting from 0% crit) - 100% -> 140% (100% crit), a 40% increase in DPS. So even when vanberk procs, it's a small boost.
To clarify for all, how the "die rolls work" - say you have 50% double attack chance, 50% crit rate. Half of the time, you'll DA. If DA doesn't proc, you'll have 50% chance to crit, so 50% DA, 25% crit, 25% normal. This means that half of the benefit from that crit rate is wasted!
What's a bit more interesting is to consider the effects of snake hat on a crit GX. With the Mora Set and 2 Aunoe cards, you actually LOSE dps by putting on a snake hat! (because DA is doing 200%, but crit is doing either 220% or 252% depending on how the 140% crit damage stacks with +% crit effects).
Edited by DrAzzy, 02 April 2014 - 01:18 PM.