It seems to be a luck-of-the-draw thing, yeah.
I know two of my Hasbro CS replacements were Shattered Glass Prime/Ratchet and SS86 Grimlock. I remember the Ratchet/Prime was to replace a Botropolis set I sent back, but I forget what Grimlock was for off the top of my head. Maybe a Netflix Soundwave?
Edit: Grimlock was actually for quibbles with Breakdown & Jet Vehicon from the Prime 10th anniversary 2-pack. Huh.