Diablo – affected by resetting quests

Chris Rasys is right.

While some achievements are character specific, the criteria for the lore and bestiary achievements (and others) are not. This means you can complete each individual task with a separate character if need be, and you will still unlock the achievement in the end.

So in this case, your solution is simple: Start a new character (of a different class, or Hardcore, perhaps!) and play through Act I again. You should pick up the missing pieces and round out your achievement.

After a little bit of research, the solution didn't turn out as I expected. First, here is how I tested it:

• For Quest-XP, I simply did the "Waiting for reinforcements" quest twice, on Nightmare Difficulty.
• For +XP per kill items, I rounded up Blood Clan Warriors with and without enlightement, as well as with and without +XP gear equipped
• For Massacre bonuses (I'm assuming that this is representative of other bonuses as well), I killed five Herald of Pestilence monsters and five Blood Clan Warriors with, and without enlightenment, as well as with, and without +XP gear two times to see the outcome.

The findings:

• None of the three things you listed had were influenced by +Enlightenment

This was weird. I was assuming that bonuses are not influenced, and that quests are not influenced, which turned out to be true. However, I assumed that +XP on items would influence it, but it did not. Specifically, the base XP I got on average from Blood Clan Warriors was exactly the same with and without +XP gear and Enlightenment on, meaning that it was the overall XP I got - the amount of +XP I got through my gear.

This means that the bonus XP seems to be calculated as:

totalXP = BaseXP + BaseXP * 0.25 + ItemXP

I think the reason they don't include Item bonus XP in the baseXP is that it would probably offer too much of an XP boost with high-level +experience helmet and gems on items, however this is speculation and something that only Blizzard can answer..