If you ask me, it should be 2hers that should be nerfed on horseback. i dont know about EU, but in NA you'll see dozens of people with longswords and morningstars 1 shotting everything, falling off their horse, and having no penalties. have you tried fighting on the ground with a spathion or a cav sword? unless you're a tank (like me), and you can absorb alot of damage, its worthless. its slow, and easy to dodge. anyone with a good italian sword or a 2h will kick your teeth in.
for the record, i fight with a spathion on foot and... well i often get outspammed, so i have to rely on brute strength. 24/12 helps, but a good spammy weapon spells the end for me.