[August]

Let's see how it would work out using the 'alternate' set of exp mods, shall we

53 Wood Elf Ranger - 40% penalty.
55 Dark Elf Enchanter - 10% Penalty

RANGER:

Total experience needed to COMPLETE 53:
53^3 * (1.4) * 1.7 = 354,327

Total experience at the START of 53:
52^3* (1.4) * 1.6 = 314,961

Total experience NEEDED TO LEVEL:
354,327 - 314,961 = 39,366

ENCHANTER:

Total experience NEEDED to Complete 55:
55^3 * (1.1) * 2.1 = 384326

Total experience at START of 55:
54*3 * (1.1) * 1.9 = 329,100

Total experience NEEDED TO LEVEL: 55,226

So in this hypothetical, Let's assume that Enchanter is at the beginning of his level, and we'll give him 335k experience. Let's also assume ranger is about mid-way through his level, so we'll give him 335k experience as well. That gives us a 50/50 split.

At 2k experience per mob, you'd each get 1k.

It would take the enchanter 55 kills to level
It would take the ranger 39 kills to level.

Let's skew it even further. Let's put the ranger at 90% in, or at 350k experience, and let's put the enchanter at 'freshly dinged' - 330k.

Each kill of 2000 would net the ranger (350 / 680) 1030 experience
Each kill of 2000 would net the enchanter (330 / 680) 970 experience

It would take the ranger 39366 / 1030 = 38.2 kills to level
It would take the enchanter 55226 / 970 = 57 kills to level

57 / 38.2 = ~1.5 - so you're leveling about 50% slower than the other party. I'd be complaining, too! (And these are fake numbers, if you're killing level 45 mobs in a ZEM of 75 you're only getting 45^2 * .75 = 1518 exp per kill split between you)