Your starting character really doesn't matter, just pick whatever you think looks the best. Upgrading Speed and Attack in equal intervals is the way to go, but late game focus primarily on speed as it gets ridiculous how fast you kill things, especially with Berserk on.
Guys, if you have trouble unpausing after your mose loses focus. Right click on the screen and go on "Settings", then press Close. You should then be able to Unpause. + this so everyone can see it.
@ Kevin
Don't both with Speartons, get one to control so he can soak up damage. Swordsmen are cheaper and faster to get out. I left Speartons completely unupgraded until the very end. Also, don't get Giants, I tried to use them as meatshields, failed very hard.
Heroic Strike should attack regardless of your basic attack's cooldown, that function makes it completely useless. Also, I really can't see the point of an axe for a Warrior, sword + shield is just so much better for just about every situation.
Guys, keep this comment alive. It's a GREAT guide that'll help a lot of people with their Amorphous+ questions. + this comment.
http://www.freewebs.com/bubblemasta/
@Dark, it clearly says "Max Level:15" on the top left corner of the skills tree.
@gary Sure, it's the most damaging, but it's also not very mana efficient.