I was at 15.3M experience and needed to get to 17.9M to get to the next level (51) and be able to put on new gear. Turned in a quest and I thought the reward was 2.3M (cool, that's going to almost level me!) Started a new quest and killed one mob, and my EXP was only 16.3M
IOW it only went up 1M instead of the 2.3M
I'm not in a guild, so none should have went in that direction.
Of course, I've wasn't paying complete attention and might not have seen the numbers right. Is there a log that can be looked at?
Based on the number of quests you completed, you wouldn't have seen a reward of anything close to 2.3 million experience. It would have been around the 1/3 of a million experience. There's no log to track quest rewards but the math doesn't support it. I'm guessing you might have seen the gold reward instead, since a reward of around 2.3 million gold makes perfect sense.
Also, as an aside, quest rewards cannot be taxed by clans .