Again, the patrons have charge in warrior most of the time, are extremely versatile in the way you can play them, the deck has a secondary combo in the way of Frothing, and 3 damage AoE is uncommon (Auchenai Circle, Lightbomb, Shadowflame, Flamestrike, Hellfire, and Demonwrath I guess, or like spell power blizzard and Nova Doomsayer). If you took Warsong out of that deck it would be far less competitive, probably a bigger hit than if you killed Thaurissan.
If coldarra drake is working in a combo deck, it needs heavy support to do so. You can't just play it and expect it to stay up unless you're already ridiculously ahead, people know what's coming. Say you Thaurissan a Coldarra drake and a maiden of the lake, you get 2 hero powers on 10 mana, not better than if you tried to combo with just drake. 6/6 body is hard to remove, sure, but it's still a risk. You bet your turn instead of hedging the bet like Thaurissan can, and dealing with Drake isn't all that different.
Maiden of the lake isn't staying up either if you play it on turn 6 or something, but it is admittedly very sticky on 4, and a turn 5 4 drop + hero power is potentially attractive as well. Priest and Zoo can probably make the most of a 4 mana 2/6, and the passive advantage generated by the ability. Priest just got its own fun 4 drop though, so I'm not sure how that affects things. The Maiden's probably one of those cards that will always be an option for a niche use, but not dominant, which is actually a pretty cool place to be. There are just a lot of good 4 drops out there, and that turn can be really important depending on the meta, so the Maiden's biggest weakness is that you're not playing one of them.