Fast Casting Problem

[slicerx]

Ok, so i bought two berzebub cards and got 45 dex thinking that would give me 96% cast time reduction. but iv got magnus exorcismus down from 15 secs to 4 seconds.
why is it not a 96% reduction? (which would have 0.6 CT not 4secs) and what would be the easiest way to get it down to 1sec cast?
i had 90 dex and it still took about 2/3 secs  =[
thank you for any help =]

[Athear Caex]

Reduction gears do not stack with dex casting. So in short if you have 45 dex, you've reduced it by 30% then the two berz clips reduce 60% of that 30%= 57% reduction so you'll get around an 87% total reduction. so you'll get a fairly fast cast time, but never get IC unless you have 100% cast reduction or 150 dex