Hmm, isn't the skill tree fixed in the fifth game?

Not exactly... If you choose different skills at each level, the next level will offer different options... Then there's Heroscaner (an obvious cheat, I've never used it)... And the simplest way is to restart the game until you get what you need...

P.S. Anyway, I'm hooked... I'll finish the add-on campaign, beat Raileigh in the original game (I curse whoever gave him such powerful skills in the add-on campaign), and then I'll have fun playing as Phaedon 8)).