It's not about the %s or the configurations, it's that his rotation logic is physically flawed at the design level. It performs well, but not top. It's one of those things that you just have to be shown to believe. People will always swear by Tuanha for raiding because it blew their mind the first time they used it -- it blew mine too. I was doing the same DPS as people 20 item levels ahead of me and I was beating all of the other healers.
It wasn't until I got into a group of people that ALL were ranking in the 95%+ percentile that I realized how much that ceiling can go up. There's performing well, and then there's godlike. Tuanha's routines are godlike in PvP, so you know exactly what I'm talking about. After switching, I began to double people's damage who are 10+ item levels ahead in heroic content. They don't follow generic simcraft rotations designed for optimal patchwerk DPS, they intelligently optimize their rotation for the fights. If you've wondered how some people get ridiculous rank 1 parses that don't seem possible, this is it.
All of that said, Taunha still performs better than almost any normal player you will find. You can still beat everyone in your raid with it, it just won't be the very best.