If they want to avoid ruining entertainment value, they should make a game that is not so easily solved by a computer program. They deliberately avoided mechanics that introduce complexity when designing Hearthstone.
I do not see why anyone other than Blizzard should be interested or required to cater to Blizzard's game design decisions.
No one is going to be "solving" Hearthstone using any of the analysis provided by the author here. The author is missing several huge pieces of the puzzle including card & deck synergy, synergy with hero power, option cards, meta-oriented target cards (aka tech cards), and most importantly, that cards themselves are a resource. You can immediately tell the latter isn't taken into account when you see cards like Shieldbearer, Voodoo Doctor, and Sacrificial Pact in the undervalued list (all low mana cards with little benefit). You won't find any of those cards in any legend-tier or professional deck at the moment because they provide very little utility or board presence. Nothing is shown in their research that provides any information that players don't already know.
He even mentions in the article that Blizzard is very supportive of their research on game and card balance, but they specifically mention that they are concerned about the real-time dashboard that can predict your opponent's deck. The prediction part probably especially puts them off considering there was a video released last week that shows someone allegedly using a network vulnerability to predict exactly what cards an opponent draws during a game.
I don't think that's necessarily true. Hearthstone is made by a well-known company, polished, and most importantly free. There's not much else to directly compare it to.
However, the massive popularity of stuff like DOTA suggests that there's plenty of appetite for games with deep, complex strategy.
There are ways to add computational complexity to a game without making it more difficult for new players to learn. Witness arimaa[0] compared to chess.
Someone who beats it with a computer program should not be negotiating with them for the release of the software. Especially with the nontrivial risk of lawsuit by a multi-billion dollar company hanging over his head.
*Edit - Just to be clear, there was no specific C&D made here. But I would definitely consider legal action a real threat when crossing Blizzard given how many times Blizzard has used legal tactics in the past. In additional to the aforementioned bnetd (which is a more defensible case), there was the implementation of the World of Warcraft clone in the Starcraft II engine that was shut down by legal action. That dude was a kid.
If Blizzard wants you to not do it, they will take legal action.
I do not see why anyone other than Blizzard should be interested or required to cater to Blizzard's game design decisions.