As far as I know the only reason to not do any balance changes before release(wipe) is that it was promised a very long time ago.
There is few things I want to point out:
every change to cards invalidate all leader-boards
every change to cards make it difficult to run replays, EA make it so you can not open them at all
From my point of view doing changes now will limit these problems after release.
Some changes like changing HP, or cost of something are for me just 1 number, and I may even be able to keep replays compatibility with some background work for these chang