So
Millhouse Manastorm. <- Epic troll. I want him on my main, which means he was definitely going to have to be the first legendary I get on my alt.
This. Card. Sucks. Like, you think it doesn't suck because on turn 2 it's really really good actually. Unless your opponent got stuck with absolute dog **** which is a possibility. Sometimes on turn 2 you lose becasue you have this in your hand. But overall it's a decent enough card on turn 2, and it usually leads to some sort of card advantage.
But later in the game it's literally the worst possible card you could play. Like ever. Ever ever. Like an extra +2/+1 doesn't mean crap when it comes to mana-efficiency later on in the game, and let's be honest when we say that there are so many things that can go stupidly wrong by letting your opponent cast an extra 4 cards in any meta deck. Like.... on principle.
Most of the value of the card is "fun", where you want to see what epicly stupid thing is going to happen to you because you played it. Which is.... fun. But not competive. Not in the very least.