You basically have to fail 3 out of 5 combines with Hasty Touch to do worse than just using 4 Basic Touch. The chance of that happening is 5%, and it has to happen multiple times (one set of bad touches isn't going to cause you to fail). I hate the Hasty Touch method but it's by far the most reliable way to do any combine unless your stats are so good that you can simply finish the item at 100% using basic touch. The only problem with the Hasty Touch approach is that when you're on your #30 or so steps, sometimes you lose track of your CP/durability/etc and end up using a move that leaves you with not enough CP to do Great Stride + Byregot for whatever reason. Sometimes I get greedy thinking I can do a Comfort Zone + Master's Mend 2 and just didn't think about how much CP I have left and that really sucks, but even there Tricks of the Trade can usually bail you out.