All I can do is ask the simple question. Who else just decided to take all the weak creatures out of there deck? 3 for an instant kill of almost any card in my deck. Ya, need to change my deck.
Well, with regard to "weak creatures"--Twister/Tornado won't be any worse for your deck than Rain of Fire/Firestorm is currently. In fact, it's even less of a threat. It's the higher hp creatures that now have the small risk of dying with Twister. So you lose some killing ability at the low end but gain a small chance of killing "strong creatures" in exchange.
Moreover, why be worried about an instant spell card when an
deck is already likely to have Owl's Eye/Eagle's Eye which can snipe your "weak creatures" out of existence
ad infinitum?