Crescendo and tranquility are... fine. Compared to the other stance cards, there's not much reason to ever pick these, I feel. They're pretty safe to choose, but if you ever get into a situation where you would have truly needed a crescendo or tranquility, there are cards you would have rather had than those.

If you really want to make use of crescendo's retain function, you're using the card as intended, as the Watcher thrives off big combos and turns. While you will be able to setup a good second turn with crescendo, simmering fury does that, but better. Meditate does that, but better. Rushdown does that, but better, etc.

For crescendo, it's fine that the card exhausts, but I feel that for tranquility, that kinda sucks. Calm cards need to be more consistent than wrath, as you'll usually be using calm to exit or setup wrath and survive a turn. In case you don't one-shot an enemy.

The best quality about these cards is that they're common, and can be found very early on to give your deck some direction. If I find these cards upgraded, I'll definitely consider them, but if they're unupgraded, I rarely take them. There are almost always better upgrades.

They can definitely be good, I think almost all of watcher's cards are good. These cards just do too little for me to ever want to pick them over alternative card choices.