I think that Blindeness and invisibility are a bit the same as far as you are in a duel.
The situation where it makes a great difference is in melee, for obvious reasons, isn't it?
So I think that what has been said about the best strategies while you're invisible stays right for blindness within duels.
The only difference if you're blind is that you have to keep protected from monsters (Goblins, Trolls, Giants, Orgres, Ice and Fire Elementals), if any are in the place, without been able to target them with your spells. That's the main difference.