Guild Wars 2

So my tailoring is quickly approaching the cap and I have a question about high end patterns am I able tp continue discovering every pattern I will need to gear myself at 80 our are high end patterns bought with karma from vendors dropped in dungeons etc etc ?

The tailor npc next to the tailoring workstation sells all the rare and exotic recipes for karma. There isnt a recipe vendor for the various dungeons, rather you purchase already made sets from those vendors with tokens. (this has nothing to do with tailoring)
The mystic forge is only important for a tailor in so far as you can learn to craft boxes of the full armor sets you previously purchase from the karma vendor next to the tailoring workstation.

They are bought from Vendors. Any tailoring vendor sells them. You are buying the inscriptions. You use those and “discover” like normal. But since they are for level 400 tailoring you don’t actually gain any xp.