One thing I don't understand is that both in-game and in this FAQ it says that completing a regional levequest as a class other than the guildmarks of the class to be awarded will yield less guildmarks, indicating that you'd recieve at least some. However every time I've done a levequest as the wrong class I get zero guildmarks.
Is there a point where you get a small fraction of the guild marks for completing as the wrong class, or does less simply mean zero?
If you swapped to the right class and killed at least one of the levequest targets, you'll get a small fraction of the guild marks, but otherwise yes, less = zero if you do the whole levequest as the wrong class. At least from my own personal experience. (I haven't tested to see if you'll get 0 for doing one of those Horn and the Hand faction leves on the 'wrong' class)
The table needs a bit of proofreading though:
Self-Preservation Gladiator Increases the length of your guard ability by 50%. 6,000
I'm pretty sure they meant 8k guild marks.
Smelting Training Blacksmith A large volume containing detailed instructions on how to make nails and rivets. 5,000
And they meant Nailcasting Training.
Mistakes on official information irks me for some reason.