We're about to fight Alexander in our Honour Mode campaign, lots of prep work first though.

R.I.P. that campaign, it happens. We've had to restart twice now. First time, we accidentally triggered High Judge Orivald or whatever his name is by blocking the pathway because we're silly and walking into range. Second time, we forgot how hard the Voidwoken jerk face hits for near those skeletons outside of Fort Joy.
Playing anything other than Honour mode is boring now, tbh. You just need to prepare better. I recommend beating the game on Tactician first and then attempting Honour mode. The Trompdoy fight is one of the easier ones. You just need to know it's coming, which is where experience comes into play.
EDIT: Also, make sure you do the content in the correct order and remember to craft spell books. There's some great combinations you can get a hold of really early. Combine a
Warfare + Pyro skill book = Sparking Swings.