Alot of old items that gives bonuses to skills got very low AC if they even have it.
Like:
http://auno.org/ao/db.php?cmd=view&id=152712
Melee AC = 143
http://auno.org/ao/db.php?cmd=view&id=152711
450 in some ACs but not in all
Also alot of OLD nice armor is not being used that much as before like Omni-pol elite, senpai etc.
Mainly I think you need to put up AC on alot of old things so they are almost as good as the new armor types.
Also I think all omni armor should have better AC then clan armor cause omni should have it. Then clan could have other benefits on their equipment like skill bonuses, xp bonuses etc.