I just finished all of the non-explorers guild gold challenges! The Paladin challenge was my last, and I managed to do it on my first try with a human paladin because I stumbled across piercing wand with about 25% exploration left. Still a close victory though!
One of the most difficult ones for me was Priest Gold, I had to keep restarting because the labyrinth RNG kept screwing me over. Not to mention I ended up using too much blackspace usually. Oh, and damn you RNG on Assassin gold, I swear it kept giving me a bunch of level 1 and 2 zombies with no whetwut before that level 5 monstrosity and nothing else. If you do it Goblin and go Taurog->Binlor (for knockback) I think it's one of the easier ones though (once you get out of that damned first half anyhow).
Now the only things I have left are the triple quests and the explorers guild gold challenges! Though, considering how difficult the silver challenges for those were, I'm dreading it