Levelling issues

I am at the point in the story were I an suppose to due The Isle of Mists quests. So naturally I’ve been cleaning up my quest log(..if I see another game of Gwent again it will be too soon.) Anyway I’ve managed to get all of them done expect for the collect em all Gwent quest but screw that I say. And I am only level 27, about three quarters of the way to level 28. And all the next set of Witcher gear is all level 29, so what gives. I mean Isle of Mists sounds like end game. Am I suppose to go into it with sub par gear cause fighting a lowly level 34 Archgriffen with level 26 gear sucked so I imagine the end game boss would be even more suckage with my current gear and character spec.

I tried slaughtering random mobs for awhile but it seems like the exp gain is extremely minimal. And according to walk through it seems like I’ve done all the quests I can so is there a way to boost my level in a timely fashion or is killing mobs for like 1 exp a kill my only way?

Levelling issues