I agree it has weaknesses, and is definitely predictable, and I'd love to see how my style does in a tournament setting. I think it's good we have different approaches.
That said, I think it's predictability is it's strength - you can bluff a throw, or not trigger the shots. De facto they'll shield, which becomes a grab opening, but if they're good eggs and spot dodge when shielding to avoid the grab, can ironically be beaten by another frisbee: frisbee{shields}->dash grab bluff{dodges}->frisbee with shot{interrupts}.
Best time to frisbee I find is when they're falling and are at a distance - air dodge doesn't work on frisbee shots if they're close together, and an air dodge on landing with no tech means a free dash attack or grab attack. Heck, even with tech, if it's a grab it usually wins out.
Needles beat frisbee (although not if they're low charge), but they don't beat can. Something I've found breaks the opener needle charge is to deploy a can and nudge to mid-stage - needles can't get past, which means Sheik either has to move up (and risk being hit by the can), move past the can (and risk being hit by you), or waiting (and allow you to jump and frisbee snipe).
Still working on breaking the vertical jump spam. I'll find a weakness yet...