I'm not understimating Usopp. I'm just basing my argument on actual manga facts. I also hope for Usopp to get considerably stronger, but for now he isn't someone who can take anything what the World put against him. He didn't show anything really strong enough for now to take opponents of Wiper's level. And I also can't agree that brain always wins against muscles. Actually it's not especially in shounen. In the first part of the Grandline Usopp's role was to be a sharpshooter (and it's only dedicated to be very precicious in his shooting) and to take out all the fodder. I actually believe for now his role will be the same. Only the level of fodder changed a bit, so he had to get an upgrade.
Ussop gave pre-timeskip Luffy a good fight, and Luffy w/ out gears was about on par with Wiper. IMO, If at this point Ussop isn't able to beat Wiper then he shouldn't be going to the new world. Sure Ussop's best at taking out fodders from distance, but I don't think that means that that's all he can do.