Neither Bul'Tauros nor Rowanne seem to be working properly. At least not the way they did before, and there's no indication from their tool tip that the boost ratio has changed. The damage they do seems like it might be scaling off the enemy's stats, perhaps, instead of my own.
For example, after I had initially attacked one opposing troop, I cast the Stampede spell. My Bul'Tauros has 57 Life, and a Stampede damage of 27, so he should have been doing 84 damage, but he only did 40 damage. On the next game, when I cast it without initially attacking my opponent, I did 78 damage. And Rowanne seems to be behaving similarly.