I do not know what others are thinking, but I think that the Baron fight is too difficult. It stops my runs every time, regardless of my comp. I hope to hear the opinions of others.
Pick better blues and spell items. ANYTHING that does 4+ damage makes ghosts easy, and they're the only real threats that fight. The baron himself gives you 1 mana for every 2 damage, meaning even regular burst, 2 damage or 2 shield for 2 mana effectively costs 1, 1.5 mana against him. It's like most bosses, if you don't deal with the adds, you're dead. Have the high damage heros focus the ghosts first