I think you guys did a great job. The only thing ruining this is stat cap at 100. Not sure if this is a bug or intentional. Capping stats at 100 ruins the whole point of faster stat changes.
What you do is this, once a stat hits 100, it becomes 10% slower to level. When it hits 110, it becomes 20% slower, when it hits 120, 30% slower, etc, etc.
Then also what you could do is increase the speed of stat gains across the board for characters that are younger than X amount of time (like 6 months). Keep increasing this as time goes on (like every 6 months, give 10% bonus to stat gain for chars that have been created within the last 6 months) then a 20% bonus for chars created within that next 6 months time interval, 30% for the next 6 months, etc.
This will allow stats to never be capped, which is extremely important in keeping people interested, but also will allow for new players to gain stats faster than veterans, so they actually have a chance to catch up.