Yes, the driver is a factor in this as well, you need to engineer a kit that will give confidence rather than take away ...
Excessive roll can mean the bump stops are in use in normal spirited driving, which is never a good thing, and stiffer springs will help to reduce required travel, but you need to consider that there's only so much travel and a point where stiffer has adverse results. Over lowering can also mean more body roll (the relationship between CoG and roll centre) and incorrectly 'cured' by even stiffer springs.