You mean like making balance changes right before the finals? Because they have done that twice already. That's actually the worst time to make a balance change but in both of those situations their hand was forced, like the Yogg and Tuskar nerf.A big problem with ladder and patching is threat on the hearthstone championship tour. I feel like they would need to rethink the HCT before any sit infancy changes can be made.
Patching before random HCT events is kinda whatever as we see card releases year round and sometimes adventure where we are seeing shifts on a weekly basis. No one complains about it because people like seeing new stuff.
The BEST time to make balance changes is right when they release new cards like they used to do (to older cards). With new cards coming everyone is expecting meta changes anyway. So when they released Karazhan, that's when they should have nerfed Yogg, Tuskar and CotW.
This is actually still faster than Blizzard's own schedule where they do two balance changes a year (with this it would be 3) and for many this is still not fast enough. You are still waiting months for problems to be fixed.