I think there should be a cap for the protection.
I suggest 2 or 3 for unupped and 3 or 4 for upped version.
And perhaps not +1 for every light producing creature, but for every second or third.
Rainbow Decks with FFQ and normal FFQ decks could become almost invincible in the late game.
This card can completely kill the FFQ god , Divine Glory and perhaps many other god decks
It would be a good effect for the Solar Shield as well, cause the name would also fit.
The creatures produce the light to protect you.
I really have to agree with the cap. I have a FFQ deck and use Eagles Eye as creature control. I have no means of killing the Queens that it had out and was good for ten turns. I had enough heals to last me a long time. But it was pretty much an autowin for it. And to me that doesn't seem fair or fun. I knew I was going to lose and no means of winning with however many turns it had left before it's sheild effects wore off. Definitely not like disipation sheild.
Here. The shield is great vs decks with no creature control, like your one happens to be. Just because you lost, it doesn't mean the shield is OP.
Also, if you had creature control, especially mass creature control, you would've totally destroyed the deck. Just remember, if you have no way of stopping something, it doesn't mean it's OP.