Enhance Regen effect is a +25% flat increase to the spell Regen.

1 point of Enhancement Magic Potency is a +0.75 increase to Regen.

Tests:
393 Enhancement = 134 Regen (168 with boots)
395 Enhancement = 136 Regen (170 with boots)
396 Enhancement = 136 Regen (170 with boots)
397 Enhancement = 137 Regen (171 with boots)


Hope this helps some of you guys! Also, as everyone should know, every 5th VIT=1 Enhancement Magic Potency.