Well, I managed to complete all the quests except Screecher Spirits, and I explored WPL and EPL, so now I only need a little less than 50,000 XP for level 50, or just over 35 Demon decks.
UPDATE: I also did Death From Below, which I was able to complete due to the bugginess of the quest. I accepted the quest, no naga came, and I failed. Then I took it again, the first wave of naga came, and when they were defeated, I completed the quest. Then the second wave (of three) came, but I had already completed the quest, so it didn't matter. When I tried earlier, there were too many naga for me to heal, and I can only heal the captain and myself, I can't heal any of the crew.
I'm also one screecher spirit away from finishing Screecher Spirits, and since you get credit by talking to the screecher spirit, I might be able to do it if I sneak up on another player doing the quest and speak to the spirit when it appears...
UPDATE 2: Got the last screecher spirit; out of quests unless I can find one I overlooked. Down to about 26 Demon decks.