No other card guarantees 70 damage for 50 resources spread over two facility types. I agree it's not the best rare out there, but getting to 25 of any resource is really not all that hard, and doing 70 damage is pretty extreme. It's a game ender whenever it's played, either as a win to the player or as a way to force a draw.
Yes, it has a terrible drawback. Yes, I only like it enough to put it one of my dozen or so decks. But not every rare card has to be equally good. I'm personally okay with it as is.
Removing the tower/wall restriction on it would fundamentally change the card from it's draw-enforcing ability, and I'd be staunchly opposed to it. Reducing the cost of either gems or recruits would make it better, of course, but I'm okay with it being just an 'average' rare. There are worse rares out there to be worried about.