I finally saved the cash to make this deck and have playing around with the first one in the OP.
Remember that Shak'Ars stopped being that effective when FGs learned to rewind and mutate BB and GP dolls. The problem wasn't the deck's speed, it was the amount of unwinnable FGs.
SoBe's speed lets there be plenty of room for anti countering (Think: leaving plenty of HP to prevent poison from killing you), so really, the only things that really screw over this deck are intense denial, intense defense bypass, and RT.
And mutation, and sometimes the fact that AI doesn't cast any creature until it can kill a GPd doll (like fractalling phoenixes, spamming scarabs and fireflies, playing and buffing any creature in general)
Mutation, leave plenty of HP to absorb, and bait the AI. I haven't seen the AI hold back creatures like you describe. SoBe disrupts fractal and encourages the AI to play something.
I can confirm that AI does hold back creatures. Witnessed it against Morte. He played three creatures in one turn (only drew two cards) and definitely had the quanta to play all of them the previous turn. The play of three creatures was enough to knockout the VD
EDIT: forgot to mention that the inconsistency of drawing a combo (especially when there's only two of each card) kills this deck. The SoBravery may get you halfway through your deck in a hurry, but too many times you haven't drawn both a VD AND a GravPull while the damage you've received is unsustainable.
Also, one FG that you won't win against is Neptune, with his congeal-->shockwave combo