Nurse Gargantuan (all other, supposedly OP cards) are generally overpowered when you play them against the right decks.
Whenever I see a thread about some card being overpowered, that tells me: "well, there's a solid card I should be using more of!" but I always find that they all have a counter when using the right deck and up to now things are pretty balanced.
Every plant deck should have some sort of hard removal, like squash or a freeze combo. Alternatively, at 7 sun/brain a good aggressive deck should be about to finish off the opponent, and if the opponent used up their whole turn to play one creature, there are a number of cards that can counter it (freezing, destroying, bouncing) while you deal the last few scraps of damage.
My suggestion to anyone finding that there is a particular card that they are having trouble with: if you can, try it out yourself and play against a highly ranked player to see how they deal with it.
If not, sure, come over to the forums but instead of posing it as a hyperbolic game design problem, consider it a strategic question: how do I deal with "this"? It will generate much more constructive answers and prevent trolling. It also helps the game designers get a better idea of how people are using the cards.
For 5 mana, you can easily make a tough beets that can kill nurse gargantuan and live. You only need to have 4 hp on the tough beets, that's 3 other creatures, and one of them is the nurse gargan already. If you can't, 5 sun creature that trades for 7 brain creature plus heal 4 is more than worth it (2 brains heal 4? That's terrible value). This card is worse than other gargantuans because you don't need squash to kill it in order to gain value, there are so many options to kill this and gain value that generally the special ability doesn't even make up for it.
I wouldn't say it is unplayable, but it is a pretty weak card for 7 brains, I would play no more than 2x, and if anything I don't play this gargantuan as there are much better threats than this card.
