Instead of encouraging/pushing us to publish work during our PhD, he is extracting the best experiments with a view to creating some uber-paper that he's dreaming of. Can I just go over his head?

Probably not but your supervisor's attitude drives me insane.
Acacdemia is absolutely obsessed with league tables, Russell Group unis and impact factors rather than good research.
It is beyond farcical.

You may not be able to over-rule him, and neither should you, because he can throw you under the bus for not listening to him. However, I suggest speaking to your co-supervisors (if any) and getting them to step in and have a word regarding publishing.