[Vedran]

Dragon's Breath, Summon Planetar and Improved Alacrity are a must have. Energy Blades and Comet are not.
Spike Trap is VERY useful, 20D6 dmg! Kills everything.
(Greater) Deathblow sounds weak, but many enemies are low-level-high-stats. I haven't tried it, but people say it is good.
Power Attack->Critical Strike->Smite is also powerful.

Assassination is powerful, if you don't have mislead, that is.
Certainly don't take Use any item, unless you want to wield Carsomyr or Valygar's armor that badly.
War Cry? If it scares, Horror is a better choice. If it stuns, there is some potential.

Additionally, soloing three-classed character is boring without exp. cap remover, because cap is hit much before Chapter 6 (exit from you-know where). I mean ToB cap.