Bungie has never shown any indication (at least to me) that they want usage to be equal for all weapons across all circumstances. They want all weapons to be used equally within their own circumstances. In other words, close range should see players with hand cannons/shotties/swords win most often, short/mid range should see hand cannon/AR users win more, etc. as it stood in the past, ARs won in virtually all circumstances, then hand cannons, and now pulse rifles. Balances try to bring each group's effectiveness in its niche up to par. This causes a power redistribution which then causes a need for new balances later. It is never ending, but it's hardly rendering everything obsolete intentionally.