OP - I run a triple on my tri cross with the lowest ring being a 22, same as most mountain bikes. In my opinion a decent cross bike can do everything a road bike can do and most of what a mountain bike can do. With that being said, a mountain bike can do everything a road bike can do and everything on trails too, lol.

I am a XC mountain biker so I dont ride jumps and grnarly stuff off road and I find my cross bike handles that terrain just fine.