OMG!! no SN's...
mark = time is better.
- graviton,
+ otyough
at least -2 towers, + SN's
SN is no good for a stall. In a rush, it owns; you don't need lots of quanta, just fast quanta. For a stall, however, QT>>SN, as it will produce far more quanta over the course of the game.
Oty? Why? Eternity does the job of CC, and PA is less situational than Quints for protecting your CC source. As there are no death effects in the deck, and Mindgate is the key card, Eternity>Otyugh - I'd much rather rewind a critter, MG it, then play it against my opponent (for massive card advantage), then have an easily neutralized CC source (Infection, Damage CC, Lobo, BB, Turtle Shield, Rewind, etc) that may or may not be useful (if your opponent is always nice enough to play only low HP creatures).
Graviton does much more damage, as well, for a lower
cost (which won't interfere with SoF's BH).
Switching marks seems like an interesting change; what's your reasoning for it? Remember, MG will be used more often, against more deck types, than Eternity...