I have friends that say similar things to what the review said.
The real problems they have with the game is they don't ever get to screw anyone over, or claim dominance of the game.
Because of that they never pay enough attention to really get the game, understand the nuances, and always try to give "objective criticism" of the game that ends up sounding dumb.
SU&SD do great with competetive games, I haven't seen them do any other co-op only games so I wonder if that was how they started off wrong.
Also they didn't have the best synergy in their team. Ra, Redeemer Fanatic, Expat and Nightmist.
They do make one very good point, and that is the point of playing Sentinels.
What do you get if you win? What do you get if you lose? Really the result of the game isn't a big deal.
The point of the game however, is not that there are tons of heroes, the point is the theme. You don't play Sentinels to beat a villain, you play it because being a hero and doing cool stuff with your friends is fun. The point of the game is just having a damn good time being a hero on a team. The beauty of Sentinels is there is nothing in the game that ruins that feeling. Yes the rules are on the cards, but they are your cards, your hero's cards. Every hero has their own rules, and those rules often let you have some great "But wait, I have this card that let's me ____" moments.
When I demo'd the game at Pax people really got into the setting, fighting to get to Baron Blade's volcanic island base, giving little care to our own survival as we desperately tried to save the Earth.
Saving the Earth was awesome, but the flip, the second half almost didn't matter. You can die on Baron's flip side and the story still rocks. 15 cards in the trash is the worst loss in the game, because it is the worst ending to any of the stories in Sentinels. In fact I think the group that had the best time was the one that had 12 cards in the trash and ended up with 3 incaps when they pulled it out. They really loved the game, largely because the story was awesome, Baron felt ridiculously powerful, and we barely pulled it off. Those fights are the most memorable, because the loss becomes more real, you start to feel the cost of failure. Those are the moments when you fall in love with Sentinels. That is why you play the game.
At least that is my experience.