And BTW, I think Chieftains tech for Vikings shall give +4 attack against cavalry AND against siege units.
When Vikings are faced to Celts or Koreans siege onagers and heavy scorps in a chokepoint, they can basically do nothing cause their heavy cav sucks
It is correct that Vikings have great troubles against Celt siege in tight areas, but improving Berserk damage against siege will do absolutely nothing to change that.