I've always done that (gear in regular bag) I have a rolling duffel that's the largest legal size the domestic airlines accept. It's actually a tennis gearbag with an external racket pocket - my Tusa's fit tightly in it. And protect that side. The bag is pretty lightweight, has wheels, extending handle and a hard plastic grooved bottom. It's been on every dive trip since 2003 (at least twice/yr) and is still relatively unscuffed. Cost me under $50 new IIRC. It takes BC, Fins, light wetsuit, spare mask in a hard case, snorkel, 2 pairs of boots, lights, a lot of clothes, extra shoes, all my misc. non-breakable gear. And still maxes out around 42-45 lbs. I often take some of my buddy's gear - he has an Akona bag.
Regs, video camera/housing, mask, laptop, plus 2 changes of clothes go in my roller bag. It's the max carry-on size. I also roll all the clothes - saves space and they don't wrinkle as bad.
I have but almost never bring a laptop backpack - like above ^ - I've been stopped but allowed to board with both.