It works extremely simply, I don't know why everyone is pumping out paragraphs to explain it.

The "Penalty" is more experience you have to gain to level.

Level 1 Warrior needs 1000 exp to level to 2.

Level 1 Paladin needs 1400 exp to level to 2.

When grouped, the person who needs more total exp to level up, gains a bigger percentage per kill.

This means whoever is the highest level in a group will usually take the most experience. If they have a "penalty" they will take even more.

EDIT: So ultimately when you are grouping, you want to be the highest level, and have have a "penalty" to get the most experience per kill. If you are the lowest level, and have a "bonus" (Warrior Rogue and Halflings) you actually get a tiny amount of experience.

SK actually levels first.

OK, well every explanation I've heard and read says that two characters who duo with different EXP penalties should level at the same rate. If that doesn't happen then I have no idea why.

wiki.project1999.org

It's based on total experience earned, as I stated previously. A level 35 war would take a larger percentage of xp than a level 36 war under your scenario.

Were you guys the same level?

Yes - the more we duoed, the further ahead he got.

The official explanation states that the percentage of XP is split by the total amount of XP you've gained to level.

I'll take a crack at showing some mathematical examples


So if a level 8 druid has 8,000 XP, and a level 10 SK has 14,000 XP, on a kill of a mob worth 100XP it is dividied up like:

8000+14000 = 22000 total XP in group
Druid is 0.363636363636364 of the share
SK is 0.636363636363636 of the share

If 100 XP is rewarded, add the 2% bonus for being in a group.

102XP total:
102 * .363 = 37.026
102 * .636 = 64.872

So now given two characters of the same level, with a normalized leveling curve of 1,000xp per level:

level 10 druid 10,000xp
level 10 sk 14,000xp

24000 total group XP
Druid is 0.416666666666667 of the share
SK is 0.583333333333333 of the share

Assuming 100xp mob normalized to 102xp for the group:
Druid: 42.432
SK: 59.466

Druid's next level is at 11,000, or 24 kills
SK's next level is at 15,400, or 24 kills

They level at the same rate

Now, lets put that druid halfway through his level.

Druid 10,500
SK 14,000
24,500 total group XP
Druid is 0.428571428571429 share
SK is 0.571428571428571 share

102XP mob:
Druid: 43.656
SK: 58.242
Druid needs 11.45 kills to get 500xp to level
SK needs 24.13 kills to get 1400xp to level.

See how the curve isn't exactly a straight line? By the Druid being halfway through the level at the moment they started grouping together, he started getting "his bigger share" much earlier in the level. That means that he is further ahead of his curve and will level slightly faster than his partner.

If both partners start at the exact same point in the level as eachother (to the infinitismal digit), they will level at the exact same rate.

If I'm wrong in my mathz or in my understanding of the mechanics, please correct me.

The normalization of XP per kill might be split by the Xp at the *start* of your current level, but not sure. That would make more sense IMO, as otherwise you run into the case I mentioned above where the person further into the level starts to gobble more shares of XP at a non-linear rate.