Last year on my road bike I was getting about 16 to 17 mph on rides - that being said, I didn't ride it all that much, I am not comfortable with it - it's too fast, too light, the traction is questionable, and I seriously hate being clipped in.
That is probably laughable to "real" triathletes - I have no delusions of being anywhere in contention - I expect to finish far, far down in the pack, probably in the 80th percentile area - and if 80% of the people in the race I am signed up for beat me, fine. In fact, dead lady is fine with me, because this is solely about me against me.
But in the bag, yes, in the sense that riding 12 miles is nothing.
Still, by not following the cycle portion of the training, I wonder about issues from muscle strain/fatigue transitioning between disciplines to whether I am missing out on learning something.