I, too, have experienced the utter BS that is the ridiculously harsh requirement for getting full credit on an S-rank mob, and I suspect that the actual reason behind this is not that the credit system is broken (though it's definitely not good, because seriously, stop devaluing damage so damn much!), but rather because they heavily limit the number of players who are actually able to get full credit in the first place. You're essentially competing for the top spots with everyone else, because there's only so many top spots to go around. Obviously, an easy solution to this would be to just not limit the number of people who can get full credit.

I refuse to believe that I can sit there, with the rest of my party, as a warrior with defiance up and an i110 weapon, spamming aggro generation skills through the ENTIRE fight, and still NOT get full credit because the party wasn't generating enough aggro. That is absolute BS, especially given how incredibly easy it is to get full credit on A-ranks (in fact, just me and one other healer or tank is enough to get full credit on A-ranks - not even a light party is required there)! Granted, this COULD be the problem if there is no cap on the number of people who can get full (and even partial) credit, but my experience tells me otherwise. Either way, this really needs to be fixed.

Hell, I wouldn't complain if simply being near the Hunt mark when it died gave you full credit automatically. It's not as if there's not enough people beating down these things in the first place!