Aiming,
all of this sounds normal : TEM2 is a game before all and doesn't aim at recreating exactly what happened in the reality ; if anything, it's more inspired from the 90's tennis when the whole top 20 players were slam contenders and had a level close enough of each others, which is much better gameplay-wise as it means your players won't get constantly crushed by the Big 4 till he reaches their level and then barely never loses against a non-Big-4 player.
Anyway, if you want to recreate the reality, you can try to fiddle with the "WT_SkillNormAtp" section in the GameSys.ini of the Modding SDK :
topic11-31376.php .
You'll have to make all players weaker using these parameters, and then manually boost all the RankPerYear of the Big 4.