It's likely just packetloss or lag that you guys are experiencing. I actually overbuffed the polearm overswing animation when I changed it several months ago. Instead of the polearm overhead hitting slower, it now hits faster than the two-handed overhead animation, and by quite a fair bit, actually.
It's not, my connection is reasonably stable and I have seen enough people describe similar experiences, there are 3 right here in this thread specifically referring to polearm overheads. I am a huge overhead whore with any class I play but I don't notice big hit detection problems with 1h's or 2h's, except of course the 2h miss and drag over the floor hit. As soon as I grab a polearm I notice it immediately and solid hits don't do shit, complete misses somehow hit. There is something structurally wrong with the overhead hit detection and it is fucked up to the point that I can't be arsed using much polearm overheads anymore. It is too unreliable and my beloved English Bill is a piece of shit because of it. Use a 160+ pole overhead for an hour or two and I think you should have noticed it yourself.
I am fairly sure it got borked when the overhead got sped up. I don't recall noticing anything before that. Perhaps there is some turnrate mismatch between the hit detection and the visual animation or something.