While I'd find statistics good to have to see how you perform, a few pointers to make the data more reliable:

1.) The statistics should be separated per job. This is kind of self-explanatory, different jobs like Paladin or Scholar will naturally gravitate to higher assists than kills, which may muddle performance when mixed with jobs that have a higher kill potential based on their kit.

2.) The statistics should be based in a specific timeframe / amount of matches. At least a split between "Weekly performance" and "All-time performance", that way you can keep track how you recently performed without feeling guilty over early bad performances.

This is a personal thing, but I'd love some way to track match statistics for the last five matches played (with names of other players hidden/initialized) since we don't have access to a replay system.