You edit your post when I was posting mine to make the same point, bastard! lol

Oh and I do agree with same level same level forever.. As long as the group is relatively the same percentage through that level.. And honestly, even if they aren't, they won't deviate much. That was the situation where everyone stays the same

Let me reiterate

Same rate: I can create a level 1 to 60 iteration of this
Converge: I can create a small time constant of this
Diverge: I can create a large time constant of this

XP is divided based proportionally on the XP totals of each group mate. If everyone has 100,000 XP then everyone gains the same xp per kill.

This means that the only time people will level at the same rate, regardless of class/race penalties, will be if they've been grouping since they started the game and never do any quests.

We can then do a calculation of (your xp total)/(xp total of the group) will tell you what fraction of the xp you're pulling in. You can then compare this to how much experience you need to level vs your group mates.

If we look at the experience table if you are level 46 you will "catch up" in levels with your level 51 friend you're grouping with until you hit 51, and then your friend will start to pull ahead again. (with no xp penalties for either). This is because the XP requirement per level for 51+ is more than double the xp requirement per level for 46-50, but the xp total is not double at that point.

So you will both converge and diverge depending on what levels everyone in the group is, and the convergence/divergence will change over time.

Edit: assuming https://wiki.project1999.com/Experience_table is true. I used 50's as an example because it is the most extreme jump in xp. Hell levels will also cause convergence AND divergence over time.

3 man group
 

20 Halfling Warrior +14.5%
6840000 xp
37 kills to level solo
22.89% of pie
162 kills to level in group

20 Human Monk -20%
9600000 xp
51 kills to level solo
32.13% of pie
159 kills to level in group

20 Troll Shadowknight -68%
1344000 xp
71 kills to level solo
44.98% of pie
158 kills to level in group

If you're at the same level you should progress at effectively the same rate.

20 Halfling Warrior +14.5%
6840000 xp
37 kills to level solo
15.96% of pie
225 kills to level in group

22 Human Monk -20%
12777600 xp
51 kills to level solo
29.82% of pie
170 kills to level in group

24 Troll Shadowknight -68%
23224320 xp
71 kills to level solo
54.20% of pie
94 kills to level in group

quickly divergent.

part in bold should be
131 kills to level in group

realized i had the formula wrong in my spreadsheet <.<

Another thought was same xp amounts. Can't edit my post anymore <.<

24 Halfling Warrior +14.5%
11819520 xp
36 kills to level solo
33.33% of pie
108 kills to level in group

21 Human Monk -20%
11819520 xp
51 kills to level solo
33.33% of pie
153 kills to level in group

20 Troll Shadowknight -68%
11819520 xp
71 kills to level solo
33.33% of pie
213 kills to level in group

Also divergent.

Try a level 21 halfling warrior, and 5 level 24 SKs killing mobs who con green to the SKs, but give xp, but con blue to the warrior ;)

I.e. the group that would never exist lol

You need to look at groups in 30's, 40's and 50's. The effect of hell levels will make the convergent/divergent properties change over the group's leveling experience. Convergent leveling would mostly happen in a mixed group of high 40's and low 50's leveled characters (ie, not until Kunark) because the xp required per level rises so quickly post 50.

So basically as a hybrid with an EXP penalty you should always be trying to join groups with people a few levels lower than you and you can sap their EXP and level relatively fast?