This is merely anecdotal (so take it for as much or little as you like) but Luke was discussing his slider on a recent Padres pregame broadcast. He showed off his grip, talked about when he started throwing it, and explained that compared to other breaking balls, his release is quite straight and easy–not a lot of torque to the wrist. So at the very least, he personally doesn’t appear to be concerned about injury.
I’ve been playing with pitch values and “pitcher luck” metrics myself(following a hunch similar to yours that may or may not pan out), and as far as my notes tell me, there is little to link SL % with BABIP or LD %. (I’d recommend wSL over SL %, by the way, as a more rounded measure of positive pitch influence). In fact, of the 4 metrics I looked at as potential luck signals (BABIP, LOB %, LD%, and HR/FB) that may or may not be linked to the effectiveness of certain pitches, those two showed the least potential of being controlled.
I’m still trying to work it out, and I could be totally totally wrong in my method, but the greatest potential for sliders to effect “luck” may be through LOB % (though not in connection with K/9)…
Let me know if I’m talking out of my ass, and congrats on the thought-provoking article (including the consideration of injury potential).