Spear Fury should be left with 1 point so you can use it for grouping as Spear-user. Polearm Crusher is absolutely useless, it's better to use Fury on single targets. I think Sacrifice does more damage on single-targets if you're PA, I'd have to check.
You don't swap weapons in mid-battle the way you described. You take the PA to Himes and you train with it. You take the spear to Skelegons and you train with it.
Edit: Currently, spears are the best endgame choice because of the nature of the Dragon Canyon maps. They're not created with small area mobbing in mind, so Polearms get screwed royally. However, keep in mind that other maps may come out.
You don't swap weapons in mid-battle the way you described. You take the PA to Himes and you train with it. You take the spear to Skelegons and you train with it.
Edit: Currently, spears are the best endgame choice because of the nature of the Dragon Canyon maps. They're not created with small area mobbing in mind, so Polearms get screwed royally. However, keep in mind that other maps may come out.