Which spot is the best to powerlevel to 200? i already completed pretty much everything up to 26.01 and my main 4 are at 110ish

while on the topic, where was it that you get the stuff to boost legendary weapons?

Personally, I think the best places are the raids, especially the special challenge of the nature raid where you fight the enemies together. The place is designed for levels 80-90, so you shouldn't have any trouble defeating the bosses. The exp drop off also very good. 

 As for the legendary weapons, you get them, again, in the raid area.

I recommend getting all EXP Up gem first and then go to act 2 for the special dungeon