I found the 4th way harder than the others (except for the boss), imo. Anubis is a lvl 37 mob (so 10 lvl above most of the other mobs) with no weakness, two powerful AoE moves (two of them and most of my team is dead) and an instant death move (so far I think only 2 out of 20 insta kill moves missed on my team...) since he's so above the "normal" level of the Palace, he acts two times in a full rotation of my team and two AoE move = dead because I can't kill him fast enough. And the number of door opening in the Palace was annoying : Open door -> Little Room with one pot in it -> Open door -> Little Room with nothing -> Open door... What the heck ?
5th Palace was a pain at first but it became easy after upgrading my gear, gonna start 6th soon.
So far the 2nd Palace was my favorite.