Mmmm. Not really.
a. Sure, it can destroy permanents, but it requires 4 quanta, and a one turn delay, and then one permanent a turn. Quite powerful, but not really OP.
b. Act as a shield. Yes, this is what makes it powerful, but not OP. I've made a deck (
http://elementscommunity.org/forum/index.php/topic,37057.0.html) based on the concept of using them as shields, and while it's powerful, not OP. It's not hard to outdamage a growing SoF
c. Using a SoF and overdrive involves 8
quanta, and takes 5 or so turns for it to actually outdamage other standard gravy attackers
d. Throwing a SoF requires at least 8
quanta for 13,23, or 32 damage. Because I have never tried using catapults with SoF, I don't think I can accurately comment on the effectiveness of that.
e. Again, have not tested chimeras with SoF, so I wouldn't know, but the idea sounds expensive, and for what?
You also forgot to mention that while
hates reverse time, it is an absolute hard counter to any SoF strategies.