Constitution and Intelligence are utterly useless stats.
Their only use is for the vitality and mana (well, endurance too, but you don't put points there just to get some endurance).
And Charms that give Mana or Vitality directly are WAY more efficient than Const or Int points.
10 points in Int or Const will bring you 60/40 points, depending on your class.
A single great charm will bring either 10 stat points or 100 vit/mana points.
Consequently, it's on average twice as interesting to put your points in strength and dext and use vit/mana charms, than to use strength/dext charms and use points on int/const.
Consequently, unless you play without patience and you won't want to wait for the first charms (which you can get almost instantly if you run to ars magicana), it's completely useless to put even one single point in either int or const.
My warrior never put a point in it, and still has far enough mana/vitality.
Note that itùs even more true of the one characteristic that's opposed to the class: NEVER EVER give a int point to a warrior, nor a strength point to a wizard.