So is it a bug or design decision for magicka to regenerate at a slower rate in combat than out (when using regen buffs)?

My pure defensive Mage (restoration, alteration and illusion) has a load of magicka buffs for regen or pool, but the way it plays, it seems only the increase in pool is worth it given that regen buffs aren't effective in combat.

As a side note, I LOVE Skyrim. Best game I've ever played.

Go with +magicka or +skill(cost reduction) . +regen's value and effectiveness (in combat) doesn't come close to matching those unless you use the regen rate mod.