From Erik Lauer:

Yes, when we lower the power level of a card, we try do take enough away to accomplish our goals, but not more. We do that so, as you say, it will still appeal to the intended fans.

Sometimes the cards still see constructed play, but at a smaller rate. For example, Engulf the Shore was creating problems at 3 mana. When we added a mana, we thought it would still be fun for casual mono blue players. In fact, it still saw a bit of constructed play; Frank Karsten finished 15^th at Grand Prix San Jose!