Just noticed this as we had the spell drop from RZ and was comparing it to the previous version.
T4 spell from Fire - Chaotic Veil of Fire
webtools/spell.php?id=8534
T6 spell from Tactics - Veil of Mastery
webtools/spell.php?id=9781
Seems the higher progression spell is only half as good and costs half the amount of mana but lasts twice as long. No real advantage to getting the higher progression spell when they are compared side by side and to their of the zones.