I would be more worried about the "d" sounds clashing in Brody Dalby. BrodyBrent Dalby just sounds off. I'm not sure if this is any better, but what about Broderick Brent, nn Brody? Broderick Dalby sounds nice.
AgreeI love the name Brody, and I would use it as a nn for Broderick. Broderick Brent Dalby sounds ok in my opinion, but I agree with everyone else that BrodyBrent is not a good combo.