I'm not writing Ponomarev off based on that but I think he has been really bad in the NHL so far.
The two have different problems, Bemstrom's issue is that he can't play at the pace of play in the NHL. He can succeed in the AHL where he has a bit of extra time to make plays and use his skills, but he can't cut it at NHL speeds. With Ponomarev, my concern is very similar to my concerns with Poulin: what exactly is he offering? He's just a generally well rounded guy without any notable traits, but generally well rounded guys without any notable traits don't usually cut it as NHLers.
That said I think Ponomarev's versatility (able to play C or W, can kill penalties, ect) will likely result in him at least having a decent career, but I'm not sure he'll be anything notable of a player because I'm just not seeing any sort of skills that make me think "this guy is a future 3C" or "this guy is a future top-9 winger".