First of all, remember that most job differences in stats will be quite unnoticeable by even the middle levels, the only exception being the hp/mp difference between, for example, a galka and a taru mage. Although you may think that tarus will make perfect mages from the start, when my bro lvled blm through valkurm, he died way more than I did (he's a taru, I'm elvaan) but in the end, tarus will have decent hp, and very high MP and will be able to survive ok, especially when tanking becomes easier.
Now a galka mage would be able to use some hp-->mp gear that will bring his MP to a decent level. Remember that race is not as important as gear, which is not as important as job.

So, if you know what you're doing any race can do any job well, just some people have problems accepting things like Galka Blm, and taru tanks (which are in fact quite good, especially as pld)