Someone at my local game shop plays Halberdiers, he uses them in a horde. Now I'm not saying you should do that as well but I've noticed that they can quite hurt anything that attacks their front, considering it aren't elite troops, if they are with a decent amount (around 25). Their weakness though is their flank. When flanked they almost die instantly, but as long as they can claim supporting attacks they are quite worth it. (And yes, his horde died because of skaven clanrats charging in the flank, no rank bonus and only 4 models that could hit back, go go ratties I'd say)