2 hours, just now (double exp) with a 50% exp potion, full group and I got 80% of a level at 45. I only had my slider at 43 (odd number no idea how it got set there). This really needs to be addressed.
You really will get more XP via quests and the Agnostic Dungeons (up to level 90 in the Agnostics). If you want to dungeon crawl, try to get all the possible quests for that zone. If you're killifying anyway, might as well get the quest XP too.
Ah! I missed that this was a TLE post. The advice about gathering quests before dungeon wrecking is still valid.
