And I must agree that, to some extent, this is not really OP. Situational, yes, but not to the extent of being OP...
You just butchered the meaning of "situational" there, because "situational" definitely does not describe a card that affects
all of the opponent's non-light creatures.
It's OP because it's basically one third the effect of a Protected Dimensional Shield for half the cards and a third of the cost, not to mention that momentum can bypass Dimensional Shield but Flare
has no counter at all. Compared to Sundial and Dimensional Shield, which need to stay on the field to remain in effect, Flare's effect can be likened more to Sacrifice's effect, which is balanced with a far more situational cost than "3 Light quanta."
The duration of the secondary effect on the upgraded card needs to be present in the card text. Assuming the upgraded card only protects Light creatures for 1 turn, an upgrade and increase in cost by 2 just barely justify this new effect. If it protects Light creatures for more than 1 turn, then the upgraded is grossly unbalanced.
Also, you need to change the "For" in the upgraded text to a "for" as you did with the unupgraded card, and reflect these corrections in the table.