[Glow=#9932CC]Believe it or not, this IS working as intended. Hariyama is one of only 14 Pokémon to use the "Fluctuating" experience ramp in official games, which requires the most EXP to level to 100; and PWO uses the same calculation as official games. The fluctuating ramp works out EXP gain differently depending on the level of the Pokémon, but after Level 36 it always uses this formula:
Level^3 x ((Half of Level + 32) divided by 50) = EXP
Because of the level being halved as part of the calculation, this curiously means that the EXP needed to reach even-numbered levels is always less than to reach the previous odd-numbered level. For proof of this, see http://bulbapedia.bulbagarden.net/wiki/Experience#Experience_at_each_level which has a table tracking EXP requirements for all possible experience ramps.[/Glow]