My group has only played four games (and only have the base set), but we have found the combination of Dinosaurs and Tricksters to be not very good, that combination being randomly assigned in two games, then someone refusing to believe there are any bad combos taking them by choice for the fourth game (which, admittedly, he could have won, if his deck was one turn faster).
I may still be a new player, but I like to think I am a quick leaner for things like this. It feels like to me that, at least in the base set, half of the factions are "support" factions and the other half are "offense" factions. Dinos, Ninjas, Tricksters (my group just calls them "Fae") and I want to say Pirates are the attacker factions, while Robots, Zombies, Wizards and Aliens are more support-y. Anybody else feel this?
To get back on track, while two support factions (Zombie Robots, for example) can be a killer combo, two attacker factions (re: Dino Fae) can be more of a hindrance. I'm not saying you can't win, but you are likely at a disadvantage.