That doesn't solve the SoSa problem for the big two decks so far that use it.
Death Stall is... only death cards, possibly with water mark for And SPlat doesn't actually need to do anything once it gets its first hit in, so it doesn't care so much about those towers, although it'll hurt it slightly. However, this gave me an idea to actually balance it that could work, I would put it in the SoSa area but I 'just' posted there and I'm avoiding doubleposting.
Make it a
Pump spell.
Base the hp cost on the amount of quanta you have upon playing it. Something like costing 80 hp as a base, but the more quanta absorbed the more the cost is reduced for that playing, down to a minimum of 20 or somesuch. A scaling effect would probably be best, meaning a 1:1 hp : quanta ratio until it goes down to 50 hp, then a 1:2 hp : quanta ratio from 50 down to 20. The ratios can be adjusted, my point is the system itself.
Death quanta
won't be absorbed but will count as 'being' absorbed, to give death that extra benefit still. So with full 75 death quanta you get to use 28 Hp SoSa's. But you had to do work to get your Death quanta that high. Also, this means that Shard of Conscience becomes a counter to SoSa! (And even 'one' helps drastically)
The purpose of this is to make SoSa take actual effort in between uses to use, or have a high start-up effort requirement. The only issue is making heavy Control Rainbows with many Quantum Towers not gain the full benefit each time, since they have easy access to that sheer amount of quanta generation, but an additional formula can be put in to make a diminishing effect for each additional element thrown into the mix if that becomes an actual problem, long as it calculates Death as highest priority.