It's more or less what StarCraft II has been doing throughout its entire existence. Every couple months (more like years these days) there's a balance patch tha

It's more or less what StarCraft II has been doing throughout its entire existence. Every couple months (more like years these days) there's a balance patch that slightly tweaks some units' stats, like build time, cost, damage output, tags (e.g. light, armored, which makes it good/bad vs something else) etc. It doesn't have a huge impact on the casual player audience, but it's enough to stir up the metagame at GM/pro level, and ensure pros continue to devise new strategies (and counters).