I know, it's weird isn't it. You can see them doing everything from roof-running in pursuit of a bad guy, to taking down hordes of ninjas for fun, to just kicking back and having a beer together at a bar and it's a perfect fit.
The fact they are so similar would normally be a strike against them to me (Hence my relief that Dick and Donna never got together), but Dick and Kurt both have a certain sense to mischief about them that adds in just that little extra randomness required to make it work,