Another thing you can go off is how it shoots. It is possible to feel if one limb is strong relative to the other. If it is way off the bow will tilt/pivot in the hand with the stronger limb being the one 'coming back'. If the limb strength is off just a little it will have a bit of a thump, if the tiller is off it is more shocky...very hard to describe this accurately as it is a feel thing. Once tiller shape and limb strength are perfect it will be 'dead in the hand'.
Of course watching any set and its position when it shows up is the woods way of talking to you. An easy way to keep track is to trace the backs side profile onto your tillering board or something before it has ever been bent. Then during tillering periodically hold the bow up to its original profile and see where it has changed. You want to follow the TBB 'mantra' of no set in the inner limbs, a little mid-limb and the rest out towards the tips. Set like this should be your goal as it indicates optimal wood strain/tiller.
These things are valuable tools when you get odd shaped limbs, one deflex/one reflexed etc...
The wood always talks to you along the way....but do you understand the language?!?!