There are three factors for dexterity:
1) Bandage speed
If you aren't using bandages to heal, then this isn't a factor for you.
If you are, you typically want dex maxed out at 125, and add in some enhancements to get 4 second bandages if you can.
2) Swing Speed
1.25 swing is the fastest you can achieve, and this is ultimately what you want with a weapon, though some heavy hitting mace weapons are worth swinging a bit slower. The higher your dex, the easier it is to achieve a low swing delay with a better weapon.
Consult swing speed charts, but you have to balance against your need for mana - this is usually the warrior's question. Strength is usually the one that gets the last consideration. You do get a bonus for 100+ strength, and of course it determines your hit points - it's always a squeeze!
3) Parry restrictions
As far as I know, the current minimum dex to be able to parry effectively is 80.
