Most EXs never get discounted. The most you might get is the $20 off coupon, and it takes months for that to usually happen. And to answer your question about sell outs, Superman. But I don't think the Catwoman EX ever made it to coupon eligible either.
Batman and Superman may have sold out quick, but not sure that was legit. Both either came back in stock or Wait Lists converted very quick. That is not much of a sell out IMO. I am talking about stuff like the P2 Savage bust that sold out in less than a day and almost no WLs converted. Seems to never happen now, you can almost always wait and use a discount on them before the sell out(and some even before the ES is set). Catwoman I am pretty sure made it as I was considering her, but ended up passing.