aim - evade = accuracy %
The problem with this formula is that it's linear and with the scaling we have, partially due to the agi:aim ratio, it allows players to achieve ridiculous levels of evade that no one can hit, regardless which class each person is.
The proposed solution is to have an accuracy formula of
aim / evade * 100 = accuracy %
With this formula, it encourages obtaining accuracy to a reasonable amount while discouraging the stacking of insane amounts of evade by decreasing the amount of utility you gain per additional evade. This also allows for the hardcore aim stackers to hit the hardcore evade stackers at a high chance.
In addition, this formula discourages the stacking of evade at lower levels, where people are still not familiar with the mechanics of aim and evade. This effectively makes any evade under 100 completely useless. It also allows for less dominance with evade at early levels, which could discourage newbies from participating PvP (not to mention all the other bugs that still exist).