I imagine resisting the control of the main Osgilliath Palan'tir involves a will save or some sort of mental ability check (or the old scrying skill).

We do know Aragorn's got decent CHA, between the ladies falling all over him and armies being willing to march into the jaws of Mordor around him. A dip into paladin for some +saves makes a bit more sense.

Even if he doesn't have a mount at the moment, why wouldn't some Pally levels make sense for Aragorn? He rode with the Riders of Rohan under a different name and guise. The only thing that really doesn't fit is he seems to have command undead, or his Relic sword grants it to him.

Granted what it also might be is elves in this setting all gain timeless body and just rack up the mental stat boosts, and elven descendants gain +6 to stats across the board (except perhaps str).