My commuter is all 105 (technically my TT is Ultegra...circa 2002), no complaints. On the other hand I have a wide ratio 9 speed MTB cassette that the bike came with (was set up as a hybrid with Deore), and a 1x9 set up would be nice. So I will think about a Tiagra in the future, maybe. I went playing in the dirt today and used the small ring on the triple, so...
I've become pretty good friends with my LBS, so I don't know how bad the damage is. But the owner said the rear brake was leaking at the lever and contacted SRAM for a warranty repair. I know there was air so I asked them to flush it out. I'm not going to argue about getting all new brakes! The old ones were X01 and I loved the lever feel.
I don't know how hot I get mine compared to others in MTB. I am new to MTB but have taken to it pretty well. I won the Kenda Cup Cat 3 series first try, I'm leading the Temecula 12 hour beginners class series (I have to run the same class all year, the 12 hour was my first MTB race). I think I was 5th fastest out of 27 in Sport in the downhill last Sunday (XC Style DH), on a borrowed HT that I've never seen, let alone had set up time on. So I don't think I brake a lot
I can say that on the borrowed bike I didn't seen to like the lever feel of the XTR. But there are too many factors there to make a good judgement.