I'm not sure if this is a glitch or a feature of the game, but when you wear the Arch Mage robes or the Mask of Morokei that have a +100% magicka regen enchantment on them they only seem to work out of battle, which kinda makes them completely useless since the majority of your time using spells is during battle. Is there a workaround for this? Thanks.

It's not a glitch, it's a game feature. Your magicka regeneration is slowed by quite a bit the second a hostile enemy detects you and the music starts playing. That's why my mage is a sneaky mage. With the impact and silent casting perk, I can kill anyone from the shadows with magic without them ever coming close enough to spot me.

Not true. All magicka regen bonuses work in combat as well. It's been tested thoroughly. The rate overall in combat is significantly lower than out, making it hard to see when your bonus is only 100%. It's much easier to see with a higher rate.

What if its +200%, should I try to get more enchantments?

Right now my 52 mage playing on Master has a robe of 125%, neck 25%, and 2 perks giving 50% total and that seems fine to me right now (+200% total). Have not bothered to do any enchanting yet.