Don't expect billmen to hold your line for long. I usually deploy them behind archers when defending. Longbowmen stakes usually soften the blow of a cavalry charge sufficiently for my billment to step in and mop up while archers are reforming.
Billmen will not last in the open field though (just check their defence...) and if I cannot hide them behind stakes, I use them solely as flankers, main body of my army then formed of archers + spears right behind them.
Dunno, seems like you're right, billmen shone much brighter in MTW, but then again I haven't had pleasure with M2TW's heavy billmen yet, they may be a bit tougher and better suited for front line service.