Int - Change gameplay constant to receive no mana for increase intelligence
Items - Remove any abilities that add to mana
Buffs - Edit the abilities manually
Other method! Do a search for a system I think by blade dk or daelin SetUnitMaxState. This will allow you to change a unit's max <life/mana> points to whatever you want. So you can force a unit to have 100 if you want.
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.