My conclusion is that level up stats for the most part is approximately equal to a character's

**base stats *.33 + torc or muffler bonus**.

This seems to hold true for all the stats as well as hp and mp although there seems to be quite a bit of variation with hp and mp. I looked at L99 Riannon with mp the modifier was not .33 but about .37 but for hp it was about .33 when I was testing with the mercs it also held true for a .33 modifier. As far as the torc bonus I have concluded that it is added separately and not as part of a direct bonus to base stats.

What this means is that if you are playing with mercs it is extremely important to use the job change function multiple times so as to maximize the merc's base stats.

I found that each time you use the job change function it seems to boost the base stats of the merc by about 10% up to a limit of somewhere between 40% to 50% bonus on original base stats. So 4-5 job changes should give maximum stat potential. This also of course holds true for all stats including hp and mp.