Yeah, your standard season order for an American drama is 22 episodes, but as hjbau points out, there’s variation with that. A season of a successful show is usually only shorter than that if there’s something like the writer’s strike, or some other factor affecting production (for example Emily Deschanel’s pregnancy on Bones shortening this season), and occasionally an episode will get pulled for some reason (Of course, first seasons are an exception to this and can often be 9-13 episodes, but that’s obviously not the case here). Having an extra couple of episodes does seem to be pretty arbitrary unless it’s built into the show’s structure like with 24, but with a show like OUAT, it’d be highly unusual to go any higher than 23 or 24 and 22 is the norm.
And hiatuses are a part of American Television, whether it’s one-week preemptions from awards shows or sports games, the mid-season winter hiatus over Christmas, or other “random” hiatuses like the one we have now. Like Hjbau said, it’s necessary to allow production to keep up, and to extend the season from September/October through to about May (and hit all the sweeps months).
They do tend to run TV shows straight through here in NZ, which is always nice, but our TV is far less seasonal than the US (Some shows run Feb to June, others May to September, and others July to December etc.) And if they did that in the US, we’d have to wait half a year between seasons, which would be even worse than a bunch of mini-hiatuses.