So I haven't had a huge amount of trouble up to this point. I beat the Castle and Forest bosses really easy and the other two bosses took a little grinding but once I found a good strategy I had their number.

That being said I can't effing beat the final boss. I've gotten past the first fight like 3 or 4 times using an Assassin but by the time I get to the second fight I end up just crumpling so hard. I know I should be able to beat him but man his attacks especially his flying swords are soooo hard to dodge. =\

I know a lot of people seem to be suggesting either the Paladin or the Barbarian, but I personally had the most luck with a Spellsword and empowered daggers.

2 haste runes and 2 vault (double jump) runes will help a lot with dodging anything in this game, including this boss. Other than that and a few class abilities, all you can do is either learn to dodge or keep farming the castle for stats.

Ideal stats are enough hp to tank about 6 hits and high damage from your spells or hits. Use the invincibility after each hit taken to wail on him.

So I might have a way to beat him.... Archmage with dagger absolutely destroys the first guy. The second guy two although the Archmage's health is a liability so you really got to get lucky on his attack pattern.

I think the Hokage or Barbarian are your best bet, but you can certainly make the others work.