Volatiles come out at night and they're super strong, fast and aware. There are tricks to help escape them(stay near water or a safehouse) but those tricks aren't always available. Also, once you engage one of them, many more of them converge on you quickly.
Yeah i got the grap hook. I'm about 50% thru the story. Recently opened up Old Town.
I play most games with the difficulty setting one higher then the default because i find it more challenging and more immersive, and sometimes there are trophy/achievements for it too. This game i wouldn't recommend doing that though...Lol. I went to lower the difficulty the other night but you can't so i'll just get through it. I just don't spend alot of time exploring at night. freak that.
My weapons are getting better so that helps.