True encumbrance, like the fact that carrying a 10lb 30' pole is harder than carrying a 10lb dumbbell, is a loosey-goosey concept that can't really be quantified into a number. I think that sort of thing has to be the DM's call.
I think that's why they stopped trying to make everything have an encumbrance value, and just stuck with weight. Weight is a very objective, easy to figure out value that easily translates into a single number, and is easily related to a character's strength.
I don't think encumbrance should come back. If you don't want your players carrying six halberds and four sets of full plate from a battle field - just tell them they can't.
-Nate