Set bonuses don't actually give the benefits with the amount of items they are showing, but they are hard coded in some way:
cast, -int, mag, str, dex - work with 2 parts
vit, -phs damage - work with 4 parts
crit - works with 6 parts - so doesn't work here at all since there is only max of 5 parts of set bonus and this is something I overlooked
Set bonuses you got from your armours are left over from 1.3.6 server, when only these stats were working, but they will be edited in one of next patches to actually reflect their benefits exactly as they are showed in game.