Im boosting my m8s sec char up fast.. he only have xp gear but still he dosnt get enough xp. He is atm lvl 45 and we just killed Diablo in Nightmare. So we missing 5levels from Hell... I have boosted him true all the quests and we have even run around killing some extra mobs. So, since we missing 5levels, what ACT is the best ACT to do again so we can start doing Hell
Act 3 > The Keep Depths is a good place to farm XP. I saw it recomended on this forum and used it myself to boost the last levels till 60. Its a good place since there are a lot of mobs in little space, so if you have good AoE damage, you can boost your XP without problems.
Kinda the prob when blizz nerf all the places where there are many mobs. Like oh no, people get to much xp and can just farm here so blizz remove all the xp you get from the mobs @ that place and they dont raise the xp you get from the quests after. Kinda sad
Problem with the keep is you often find yourself walking in empty rooms for ages, the idea is to be in the action as much as possible.
I was doing this with a friend about 2 days ago. We got him to 60 pretty quickly, tried loads of different runs and this one took the cake:
Start the first quest in act 3 and walk to the start of it (where you will get a check point), run this part of the map for about 3 minutes until the big groups are down then start the game again before going into the next part of the quest. You will appear at the checkpoint and kill the big packs again. This was at least twice as fast as the keep if done quickly enough (I used a Wizard since it was very fast to kill big packs but any kind of AOE attacks are good).
Once level 50, go into hell and do the same thing to 60, hope this helps