Yes it is open. But don't worry, we've beta tested it thoroughly, its very hard to kill the driver. However, stay away from church towers if you're using it. Commander sits nicely down inside the turret (unlike m36 jackson in FH1).
Bottom line is, the enemy will need a major height advantage in order to snipe you. If you're in an open field you have nothing to worry about, just as safe as any other tank. Trust us on this one.