Just wanted to report: GA's #2 player picked up Sheik a couple months ago and has really come into his own with the character. Last week I played him in two Finals sets as Wario and won 3-2 both times.
This is relevant because a key part of my victories was the Ground-Only glitch; DI away from Sheik D-Throw and then try to SDI in the opposite direction (for example, for a Sheik facing left, DI the throw left, then mash quarter-circle motions up-right) in anticipation of the U-Air. While he tried multiple times, he didn't get me a single time at KO percents because of this.
Though this is a relatively small sample size, it appears to be reliable and should help our chance against Sheik by a good margin, since we no longer have to fear grabs at 100+%.