JK, I only go into the hills when I feel like doing some climbing, if I don't feel like it and want to train LSD or recover , I stay on the road or do some flatter circuit. On the road I use a set of wheels with a DA 12-25 cassette anyway.
In races (marathon stuff, no XC) I usually have a granny , not because I cannot climb the hills on the middle ring, but to prevent me from going into 'power mode' all the time, sapping too much energy . I use the granny to be able to relax a bit while on longer climbs. I know it sounds a bit funny but you actually can recover on a climb
It's a mental thing as much as a power thing. You have to believe in yourself and try to make the climb on the longer gear. You'd be surprised what you can climb on a 34/34 gear !
You need a good eye and the ability to stop pedalling when the traction is worse, and re-engage pedalling when the wheel bites.. it's quite a challenge sometimes but that is what mtb is all about, is it not.
About the traction thing, the lower the gear you are in, the more likely you are going to start to stutter over pebbles and stuff, I feel you can correct loss of traction easier when in a bigger gear.
That being said, if you are on the granny at the beginning of a tough technical climb (say you're pushing 22/23 or something) you can always shift up a few gears (say to 22/28 or something) to take you over a steep part and then shift down again to a longer gear to continue the climb. If you are already on the 34/34 there is no other option but to push hard and try to grind it out ..