I have the same 18BH as you. Prior to it, we had an Oasis 25BH which requires a WDH. When we decided to trade down, my intent was to use our WDH (Blue Ox), but weren't able to. The Blue Ox requires a 2 5/16" and the hitch mount on the 18BH is a 2". However, after hitching the 18BH to our Yukon XL and hauling it home, we had no issues. Granted on extremely windy days, you'll feel it, but I don't believe it's anything dangerous. I would agree that mirror extensions would be helpful, considering our tow vehicles are on similar chassis.
2016 Shasta Oasis 18BH