I have played all 3 classes and have found it much easier to focus on just ONE class. Using my creature with a (Magic Missile/Magic Blast HEAD) Personally, i never waste my skill points in the ghost,undead,skelly tree. My suggestion is to pick a class then bring up 3 skills so it doesnt take you too long to get them high enough to do major damage. Spreading your skill points around in 2 or more classes just gives you alot of weak skills.
Warrior = str 2, dex 1, int 1 per level up- occasionally vitality
Mage = int 2, dex 1, spirit 1 per level up- occasionally str, vit
Ranger = dex 2, str 1, int 1 per level up- occasionally vit, spirit
Warrior definately max WHIRLWIND, Evade

Mage max Magic Missile, Fireball

Ranger max Explosive arrows

These are just some suggestions from my own experience and play style and all have worked great in completing the game on the 3 classes

If you get swarmed, just run back and inch your way close to draw one or 2 mobs, then back away a bit to fight them , those chiefs are NASTY but doable solo+ health pot
