Actually, after calming down I don't see this deck as that frightening. This is exactly was I was to balanced. This deck is more vulnerable to cc than cremation rush, so it should be compensated with a little more speed in return. Players should make a ttw study and see just how much faster it is to truly balance this card. If the results are too good, +1 cost should fix it.
Now someone should make a Dragon/Mitosis/Sor/Quint FG killer and see if SoR is broken again. Sadly it won't be me, I'm busy.
Edit: Alternatively, instead of a cost raise block Mitosis from Copying Weapons. It would be a shame to lose this, but it's a potential overkill. However, we are talking about a 3-card combo that can be nullified by a single cc card. Maybe, it's not so bad.