First of all, Nourish is rated 55 on Heartharena, making it barely even average. No one plays nourish in arena, as it is almost never the best pick. Additionally, Mana Tide Totem (also rated pretty low on Heartharena at 59) is a totem. There are synergies, buffs, etc. that you can play is your deck which can interact with it, making it infinitely more dynamic and useful than a 0 attack weapon.
You also will not be “drawing cards until the end of the game”, you will draw 3 cards at the end of your turn for 3 turns and it will break.
Even if this card is average in arena, there is no way to justify a 5/5 rating. You do not pick this card over most other legendary minions.
In my opinion, even in constructed, this card will fail. It has no place in a control mage deck, for fear of overdrawing/fatigue, leaving one other option, tempo/secret mage, and unfortunately it’s just a terrible tempo play, plain and simple. I predict that it will see play briefly, and then it will stop being played as the list is perfected. Just as the Hunter and Druid quests failed, and the Mage DK faded out of play (played in hardly even 40% of mage decks according to Hearthpwn), this card will fail too.

I think he meant you can get this minion from evolving dopplegangers, because it is a 6 cost minion. This is just another sick minion to evolve things into

Have you ever played arena? The only way you could ever afford to play a 6 mana, 0 attack weapon with no immediate effect is if 1) you are already ahead on board and your opponent is low on cards or 2) both players have an empty hand, empty board, and you happen to topdeck it. Even then, I’d much rather topdeck a big juicy legendary minion than this card.

Easily a 1/5 arena card