I tend to think that your approach is probably for the better. What I think happens in Yoga when there are 'performance' goals is that the emphasis tends to be more on touching your nose to the knee, rather than feeling that deep stretch in the muscle. Feeling the stretch is really where the benefits are. I think when people are trying to hit benchmarks, they tend to lose good form in order to achieve a concrete result...It is hard because many of us like the sense of achievement that comes from reaching a concrete goal.
I think I have to accept a certain level of vagueness within Yoga.
I'm also with you on incorporating balance poses. It's hard to know how much is enough, but I'm guessing that 5 minutes of balancing with full concentration is better than 30 minutes of balancing with a wandering mind.
I think with balancing, other than the prevention of falls, there must be other benefits that are difficult to know and hard to measure. Perhaps the brain functions differently when a person's balance is well-developed, but it's hard to know. It reminds me of a saying I once heard a person say; that in essence they don't know how electricity works, but they know how to use it.
I think well-developed balance does something very positive to muscular and athletic development. It's like the difference between a bodybuilder and a gymnast. The bodybuilder may have larger and stronger muscles, but the gymnast has not only strength, but incredible control and athleticism. It's as though muscles develop in a very efficient, symmetrical manner.
One thing that I have found very inspiring in swimming is the feedback the water gives. I may be a little out on left field on this, but I think that when we become more efficient and hydrodynamical as swimmers, we are positioning our bodies in the most healthy postures and movement. Something that is much harder to get as feedback while doing Yoga.
I have this other theory regarding swimming that may also be out there, but I tend to believe that when we learn to be hydrodynamical in the water, the muscles develop in a very aesthetic manner. Swimmers tend to have shapely physiques. More so than runners and cyclists in my opinion.