I think it kinda would make more narrative sense to require the revivify spell to be cast within a minute. FIxes the "loophole" well enough for me. The game could stay in turn-based mode and give you ten rounds after combat ends if a party member is down.
Personally, I'd give you an item rather than having all of these scrolls everywhere. Maybe something from the mindflayer ship and have it linked to the tadpoles, even -- although I have no idea if that makes sense with whereever the plot is going to go.
