In order to be successful I believe most posters here would agree (?) that you want to develop a "repeatable swing". You want to develop your mechanics so that you always know where your club head is, you do this by having a "repeatable swing", without good legs, a good base, you will not be balanced. Therefore you will never know for sure where your club head is. With good balance which may help lead to a repeatable swing, you can make minor adjustments in timing and swing plane as you read pitch location. This I believe is critical in sustainable success at the plate.
I also believe that if you do not have balance at the end of your swing, you may be hard pressed to obtain consistant repeatable balance while in the middle of your swing. It is very difficult to verify good balance during a swing but quite obvious at the end of a swing, especially for the hitter who is ultimately responsible for critiqueing his own "at bats".