Well, there is endless debate on the whole topic of double weapons, particularly the Urgrosh and Double Sword, though the other two bother some people as well. Some people feel they are simply overpowered, particularly in the hands of tempest fighters, TBF rangers, and rogues (well that covers pretty close to all serious melee classes right there...). Other people feel they are just OP in the sense that any character who would contemplate using two weapons would be crazy not to take a double weapon. Then there are those who just don't have a problem with them.
If you fall into category 1, then banning them is basically pretty much the reasonable response.
If you fall into category 2, then there is room for various tweaks. According to one statement made by the 4e design team they had intended double weapons to act entirely like 2 independent weapons with different types and with the off-hand and defensive keywords on the "minor" end of the weapon only. Apparently the goal was to give two weapon wielders a way to not be forced to keep up with 2 magic weapons by allowing the enhancement bonus to apply to both ends. So that would be one approach. It definitely has a slight impact on tempest fighters if you do that. They'll loose 1 point of damage with the "main" end of the weapon and RoB will have to do d8 damage. It will have basically no impact on rangers and rogues though unless they're MC to fighter for RoB and even then as I said before the difference is not that great.
I guess if you feel that double weapons are STILL OP, you could drop the defensive property. However that pretty much puts them exactly on a par with wielding 2 military weapons, so rangers might as well not bother. Rogues might still be interested though. It would cost tempest a point of AC, but otherwise doesn't really give them much reason not to keep using the urgrosh since RoB/spear stuff is the whole point anyway really.
