Your weapon delay cannot fall below 1.5, regardless of how haste- and quickness-buffed you are.

Every 10 quickness you gain from 50 to 250 reduces your weapon speed by 1%. Increasing your quickness has a positive effect on your base damage over time BUT it has a detrimental effect on styled damage and all damage adds.

The net effect is slightly improved damage at the cost of having lower front load damage and higher endurance costs to style more often.