Bad shielders will easily fall prey to fients/holds/kicks, so you don't need to break their shields anyway.
Good shielders will either put their shield on their back if you whip out an axe, or let you break their shield then block fine anyway.
You are better off just using your spear all the time. Speaking as someone with like 140 mil of XP as a shielder, an instastabbing spear user is way harder to fight than an axe/poleaxe user.
That said, Long Bardiche is a devastating weapon in any circumstance. I don't know why it isn't more commonly used.