SoF is still a pretty good permanent control card for all colors without normal permanent control.
Because rainbow decks can get it out very early (and very often), I think another nerf is good.
I´m still for starting at 0/1 and dying with 0/4. gaining 1 HP per destroyed card.
This will also create a new synergy: Infection, and a bit Drain Life/Icebolt. Infect one shard, and it could stay forever, but most CC stops it. Even Blessing.
Except this, there´s no real way to weaken the HP of the card without a downside of the used CC. Use Icebolt , it may freeze, try Drain Life/Icebolt, you may have too much quanta.
Activation cost ? Maybe random quanta.
Voted for "other".