I really don't think it's a bug. Magica regen% gear still affects your regen speed IN combat, it's just slower than out of combat. If we had the out of combat regen speed all the time then mages could just cast endlessly with no thought at all.

I wouldn't mind if the in-combat regen was a little quicker but not by too much.

Try testing without the mask on, iirc the masks count as either heavy or light armor and this might affect regeneration speed. (if so then this makes the regen mask useless?)

It's not a bug, it's a balance thing... like Aramyn said, if it stayed the same in combat you could cast endlessly. When we get the mod toolkit I'm sure there will be a dozen or so mods that all do exactly what you're asking for, but I warn you now it's going to feel like a cheat once you see it in action. And I don't know anything about armor slowing magicka regen. Where are you getting your information on that?

Honestly, if you were getting 200% magicka regen in battle this game would lose appeal so quickly. Putting most points in magicka and getting decent perks already allows you to basically roast everything in the room by level 20, having unlimited magicka basically takes all challenge out of combat.

No its better to kill one dude and then kite for 1min. then kill one more

Yeah see we're talking about higher levels, not level twenty. -.-

Magica regen is 3-4% of your magica pool so you recover 3 mana on a 100 mana pool or 9 mana on 300 mana pool.

a 200% magica enchant will up that 3% to 9% so you will recover 9 mana for 100 mana pool and 27 mana for 300 mana pool.

To get 300 mana you would need to be lvl 21 and by then you will use master lvl spells that are costly even with the %50 less mana perk and the 50% bonus to you get from having 100 skill points in a skill. Destruction spell enchants/potions/skills/perk dont stack like all the other skills so you wont reach a 0 mana caster without enchanting a 100% less mana gear.

I got 100 skill in destruction and perk for apprentice 50% less mana and chain lightning still cost me 65 mana to cast. With 27 mana per second recovery I would still be burning mana ridicolusly fast and the higher lvl spells will be even more costly. I dont use any less mana enchants on my gear so im only using the skill and perk bonus for my spells.