I've been thinking that Great Weapons, especially once mono'd, are ridiculously too powerful. 2d10 + SB is more damage than a Heavy Flamer; much more than a Power Sword. Their only downsides are weight and the fact that you can't parry with them. So, I've been thinking about how to better represent the "HUGE BUT CLUMSY weapon."
My idea is to represent that you need to use big, powerful, easy to avoid swings. I suggest that 1) attacks with a Great Weapon can only be made every other Round (since you need to spin the thing around), 2) cannot be used in conjunction with Swift and Lightning Attack (same reason), and 3) opponents get a +10 to Dodge them.
What do you think?