An interesting distinction (one which allows for more intelligent "playing against" options) might be having it drop to Perm status at end of turn instead of instantly when Cloak is lost.
That way, with 4 HP, someone can double up on RoF in one turn (or follow RoF with other CC) if he really, really wants them dead. Which may well be the case if you have 8 of them on the field due to PU or Mitosis.
So it'd be like
(own turn)
PU x2 on some of your existing Weeping Angels
(enemy turn)
RoF, cloak dispelled, 3 x Fire Lance kills 3 Angels, the rest despawn into Permanent form at end of turn. Then you can re-cloak next.
Alternatively, the Permanent form could potentially "remember" stat changes such that when they go back out, the ones that were RoF'd only have 1 HP.
My 2 cents, I prefer options for intelligent counter-play to exist, especially if it's not easy or takes a couple cards to do. My way, Pandemonium MIGHT counter the Weeping Angel in one card, but RoF requires 2 cards and is a guaranteed counter.