The mc sounds like he'd fit the DQ description of a Sage. Has healing magic, offensive magic, can fight on the front line and not as good in any one of those areas as a more specialized person. Even so, it means he brings a massive degree of flexibility to any fight and can adjust to fit a number of different roles as the situation demands. On top of that he is good enough to be an S-rank (there is a reason their are so few of them compared to the total number of adventurers) and is capable of strategic and tactical command in a fight. And they want to kick him out?!? All I can say is I wish I was there so I could try to recruit him on the spot (and treat the other three like non-entities while doing so).