One thing for people concerned about particular pets giving an unfair advantage:

One thing they mentioned was that each Minion has a 'cost' which goes against a total quota of minions you can field at the same time. The stronger the minion, the more it costs. That means that even if one minion has great abilities, the opponent could be fielding 2 - 3 weaker minions for the same quota cost. So you can have a couple of really strong minions but your enemy could be fielding a lot more minions than you and since this game involves defending locations, being very outnumbered could be really bad.