Sir Brennen
Legend
I'd have to say it sounds like your combats ran long and required a grid due to elements you introduced into the play test, not because of anything in the play test rules themselves.
Specifically, Facing introduces a whole host of game slowing, grid dependent elements. Charging and flanking were also added elements. Adding in an ongoing disadvantage for all your NPCs also involves a lot more die rolling. (Personally, I'm thinking of allowing at most one non-stacking minor penalty or bonus to rolls independent of Adv/Disad, so your light sensitive monsters would have just had the same penalty as 3.5 light sensitive beasties: a -1 to attack and Spot/Search checks.)
Specifically, Facing introduces a whole host of game slowing, grid dependent elements. Charging and flanking were also added elements. Adding in an ongoing disadvantage for all your NPCs also involves a lot more die rolling. (Personally, I'm thinking of allowing at most one non-stacking minor penalty or bonus to rolls independent of Adv/Disad, so your light sensitive monsters would have just had the same penalty as 3.5 light sensitive beasties: a -1 to attack and Spot/Search checks.)