Double-tap 'w' key before you attack; this gives you a stun buff.
Double-tap 'a' and 'd' to dodge an attack.
Double-tap 's' for an evade buff - especially just before running.
Do these after any combos and spells have cleared. a, d, s is especially useful if your health is going down and you are in a group - I have actually been able to circle around the group just by double-tapping, avoiding major damage while my health recovers and the enemy keeps taking damage from the rest of the group.
Everyone please add your experience with this - we can all learn something new!
And remember this always: FoS...ftw!!