Both cards are overpowered for a few different reasons. I'll admit I'm fairly new to this game, so I could be wrong, but I'll list a few.
Darkness becomes all of a sudden able to use all permanents, spells and creatures in the game without splashing in another color, just add photons and sacrifice. Imagine, a darkness deck being at low health, and all of a sudden it casts miracle. Or it's being screwed by an army of fireflies and it drops a RoF, how can you possibly be prepared for that type of thing?
Lamb has a very similar function for light.
Upon further thought, I'm not sure that the cards quantum saving mechanics will be a big deal, but the way they allow these colors to have access to many other powerful cards without splashing in other colors makes them potentially very overpowered.
One of the things I can have a lot of confidence in while playing is while I'm playing a mono-green deck or a mono light deck I can expect no permanent removal or creature removal, entropy and death has no permanent removal, earth has the only earthquakes, gravity has the only otys (well scarabs maybe, but they still need gravity quanta) etc...
Colors have certain capabilities and limits, these two cards would remove these limits to a certain extent from darkness and light decks.