perhaps it is taken into account in the sense that quag dispells 2hq and incAgi and reduces Aspd beyond that to the extent that whatever Aspd you gained from berserk/frenzy is negated by it.
I play my wife's LK. I zerk all the time, and i use zerk pots. I've encountered quag, and yes it does reduce Aspd from berserk but no, if i was zerking and used a zerk pot i'd get base Aspd + zerk pot Aspd and if i went into a quag just with 2hq and a zerk pot, iirc i still got base Aspd + zerk pot Aspd - a wee bit from the quaq. So it all adds up i suppose... will try it out later tonight when i get on.
and although i would love to get zerk dispelled on quag, i don't think that will ever happen... as jugg said, dispell = LK could tele or survive somehow, but quag = death...
-w-