Interesting discussion here... I would think that any type of swordsmen (Hastati or Principes) would whip up on spearmen even if they are in a phalanx formation. However, I have not tried this myself so I would not know (I am currently playing as Scipii and don't face the Germans yet).
From what you all are saying, this is not the case.
How about using velites against them first? After this, distract them with a hastati or town watch with a frontal assault while coming around back with horses/principes/triarii. Or, even better, get many Cavalry Auxilia to just harass them to no end. Then use other units to finish them off.
Just some suggestions.