I thought you took an attack penalty for being blind. But perhaps more importantly, you don't just need to guess where the enemy is, you need to guess where your allies are too.
Blind does not mean you have a -5 penalty to hit. It means enemies have total concealment. This is a massive difference in the rules, because powers and similar that ignore total concealment are unaffected by blind. This is a crucial distinction in the rules and one I've had to explain many times now lol.