It does bother me that fragger is the best duel merc in the game but i could live with it, on the other hand he is also the best at killing groups which i simply cant accept. He can wipe whole enemy team with k121, he couldnt do that with m4 (simply because it have lower magazine size + lower damage per bullet) and when you add grenades that are almost impossible to avoid its just getting frustrating.
I also do agree that he probably looks more overpowered then he is in reality because of the maps/bad audio (like really bad, especially because of that hit feedback) but it would probably be easier to tone down his grenades for now then change maps/fix audio, especially that maps are a hot topic for years now (no idea about audio, but at least it was confirmed that they are working on it
).
Nader is also an assault class but i never felt that she gets tons of cheap kills. She is pretty weak in duels, cant make a good use of her grenades in open space and while she is decent at clearing chock points you can still avoid death and fragger is better at this. To put it simply, nader does offer counter play, unlike fragger and they are both in the same merc class, this does bother me a lot.
I do belive that at the very least grenades should be nerfed, in worse case scenario he could be rebuffed if nerfs proves to be to harsh, its f2p game after all