Shriek of the Impending Shafts

Its a lovely spell for the more militant magi, Shriek of the Impending Shafts allows your magus to hear incoming wooden weapons and take appropriate evasive action.

Its only herbam and says wooden weapons, so your quarterstaff, cluff, cudgel all seem fine, but how about an axe or a spear?

An axe has a haft most likely made of wood, as does a spear and a spear is far more wood than metal. How about a mace with a short thick shaft of wood?

Does this spell in fact allow you to sense most weapons? I can only think of swords, some maces and mace/chains as weapons without sufficient wood.

Does this seem like it makes the spell a bit too useful or not?

I think the fluff in the spell text is important. A piece of wood that is controlled may change course, so it is sometimes wrong. I agree it does work with anything that has a wooden component. It's most effective against arrows, allowing one to automatically dodge them at 10+ paces. +9 defense otherwise seems reasonable, too.