This is a tough situation. We want to make it more powerful/synergize well for mono/duo gravity compared to using it in "other" decks. Problem is, any changes made for upping cost, whether it be casting cost or activation, will hurt EVERY mono/duo, including gravity. Reducing HP gained per activation and "max" HP before turning to BH could possibly help CC, but, again, takes away from gravity synergy. This card is unintentionally most powerful in rainbow decks, far more powerful and flexible and easy to play in rainbow. Most decks have one shot at removing the focus threat, after that one turn, strap in and hold on 'cuz it's gonna be a bumpy ride.
I used to gamble with my permanents, with the previous PC available. Now, in my rainbow, I have adjusted my metagame and I ALWAYS pack 2 PA's. Some matches, 2 PA's mean 2 dead cards, and I'm ok with that, because ANY deck can have PC now. I don't want my skull buckler stolen or smashed, usually. Skull Buckler destroys dark and fire monsters. If I see gravity quanta, or devourers, I'm going to PA my sanctuary. Earth quanta, my towers are getting PA'd. My Poseidon ALWAYS gets a PA. Chances are, Poseidon isn't leaving my hand until a PA can immediately follow it. Point is, Focus can EASILY win games for someone. Other side of the coin, so can my 1

PA.