sure! I'm not saying one character was built wrong, or the other was min maxed to be superior to the others. What I'm saying is, the rogue is not just a rogue, it is a MC, the gives him a lot of raw power. It should be acounted for. The fact the fighter went for defense should be observed to...
It seems to me that your rogue was built to do a lot of damage, and your fighter was built to be defensive. And that's what is happening in the game. If the fighter wanted to do more damage than a multiclassed character focused on dealing damage (even if it is not the best MC build for damage)...
I'm not that familiar with Greyhawk, and was under the impression it was fairly similar to FR in genre and mechanics, being more of a "standart" fantasy setting. Am I woring in that? what an adaptation would have to include? What makes 5e as it is now unfit to play a Greyhawk campaign? Would...
well, for 5e's parameters, he has power-gamed the character. What I don't understand is how the fighter is not dealing more damage than that? sure assassinate is awesome in the first round, but action surge is equally as devastating...
Maybe that's the best way to go at things... Instead of changing the class in a tricky way, and risking a player feel you robbed them of their powers, trying to find a justification that fits your fiction of the world.