You might have just gotten an unfortunate bracket. If you can't benefit from SR at all, just keep doing UR until either you break through to the finals or you get lucky and get a matching UR.
Edit: Also, from what I can tell, you receive less experience from two cards if you train one into the other, but more if you combine them. I've only done one test each on these so I'm not 100%, but if the experience is consistent then it looks like you should always combine lower leveled cards when possible before feeding them to a higher card. If this is right, then it might be worth waiting on feeding any rares or above until they're combined to maximize experience gained. I'm not sure yet about how to maximize experienced gained overall when waiting on finishing a KotR to feed whatever you win, but for now, my plan has been to just use any obsolete max pro cards first and then any other high-level cards that I've fed that are either pro or whose pro I already have in my catalog.