So far? Below admirals it seems and probably weaker than most YC1. He has 2 hax powers, the eye attack which we now know isn't working well against decent opponent with Sanji and then Luffy tanking it without any problem. And he can also immobilize people, we don't know yet how this one work, but it probably involves range and a limitation on the number of persons he can immobilized.
Other than that he is a punching bag, has no mobility whatsoever, weak haki. The regen is probably linked with the Ope Ope no mi powers that gave the gorosei immortality.
But his strength shouldn't affect Gorosei as a group, for all we know they could be stronger than him with better dfs as well.