Eh, it's unbelievably tough by normal standards but bear in mind this is supposed to be a trained Dark Jedi. The fact that it slowed him down that much - enough to do so badly against a Storm Trooper and then lose against an untrained force sensitive who discovered her powers this morning and has never touched a lightsaber - puts him kind of below average for what he's meant to be.

That said I think it's all intentional, on the writer's part, at least. Notice how his name's Kylo Ren - not Darth Whateverhesgoingtobe. He hasn't been made a Dark Lord yet, so I think that he's still to the Sith as a Padawan is to the Jedi. He's lording around acting like he's the boss of everyone, but he still hasn't passed his Sith's mock exams. Essentially he really is just a whiney kid right now, because he has as much to learn about the Sith as Rey does about the Jedi.

Exactly. You can be tougher than a burnt steak, but if your emotionally a 12 year old who isn't capable of emotional intelligence and is a stalker for someone long dead going to the point of wearing a mask to be more like him, most people consider you a whinny bitch.