What would be the best Job to cap at level 50?

I'd suggest a DEXless sin. ;o You'll be able to own right Rombots and the multiples monsters in LPQ. The only difficulty would be the lack of ACC, though. So, good gear will really help. LUKless Clerics work too since you'll be able to both do higher damage than other Magicians and use Heal as well. Pretty much a plus in LPQ too since you'll be greatly needed for boss stage.