After so far playing through and feeling the bosses are easier than getting through the normal mobs, I met Radahn.
This guy can get fucked, dodging his arrows at the start takes extreme precision, dodging his volley of them or his bloody meteors is basically impossible and they're 1 hit kill moves. you either have to hope they target an npc instead of you, or they get in the way or he's in a position where the topography gives you slight cover at the right angle. It's pure fluke, 1st go I got him to within about 3 hits and his floating meteors took me out without warning. I then spent countless tries just getting 1 shot time and time again by things that are impossible to avoid even after putting on all my best gear to deal with him specifically. Eventually had to go away and put a tonne of runes into different attributes I had ignored to be able use rot breath like most of the Internet is suggesting. It trivialised the fight but I shouldn't have had to go down that route.
I feel like the game really really wants you to play as a magic build the further you get, bosses and enemies become so much harder for melee builds and the armour with no upgrading available all but becomes irrelevant as most things are going to 1 or 2 hit you anyway.