building an assassin:
get spectral dash as soon as possible. that is an area-attack, so it is good, and no need to level immensly. Put points into Adrenaline when your focus starts depleting during the fights.
Aim to use Spectral Dash be useable as often as possible (quickening, second point in sahdow reflex).
Give it more damage with Cruelity.
Get Mirage during the endgame.
Get more survivaly skill with 1+ point in Defensive Reflex.
Pretty much the only thing an assa needs is agility. Defense and vitality don1t hurt either, but the rest are dump stat.
Kick and Spectral Dash are both able to disrupt casting. Get to the enemy fast and keep pushing in melee. That's it really, not much different from a warrior. Slightly harder during the game (call it more balanced), and somewhat easier against .. forgot the name, the boss in Sharuda Fortress final area) shooting poison around and has a very strong punch beside that. Now while with warrior the game is almost a cakewalk, that guy is just a pain for him as he can float and is fast so the warrior's Heavy Armor skill hinders there a lot.
Warrior: get Brutal Advantage at the start, then go for Avenger. You'll want Deadly Charge for endgame (cool thing is there is no 3 point in the prerequesit skill requirement for it unlike the other classes' ultimate skills), but before that you'll want a second point into Concentrated Brew, and Lasting Pain should be invested into too. Dump the rest of the points into Heavy Armor (put more point here if you don't like Lasting Pain for example).
Warrior needs weapon damage, strength, vitality and defense in this order with the above build.
For most enemies use the special moves as regularly as they become avaiable, and against special bosses restrain the special attacks to be able to interrupt casting.
Against the fireball throwing female boss just wait until she shoots the fireball, then jump up/down on platform to avoid the ball, and when it passed jump right on her and do a disrupting attack to prevent you being hit in return. If you ever get into trouble you may run to the other end of the room (the room is very hugh) and just stand there and get healed.
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The above builds were tested on Normal diff, but appeared strong enough to deal with Hard as they usually had 3-5 unspent skillpoints until lategame.
Any advice with an inteligence/focus built priest?
Planned skills: Soul Shatter, Summon Shadow, Energy Field with support of Dark Impact and Insight.
Ability-focusing skills seem interfering with the core idea of shooting, but if that's the only way I'd accept it. Phasing Spirit and Decoy seem a waste. Meditation is so slow it not worth a skillpoint as it's just an unlimited food supply if you ask me (15 second casting time???).
Seems the starting area is only solvable with a slvl 1 Summon Shadow. The White Forest might be passed with that too if you have persistance to wait for some luck. But Bandit Camp I found no solution until now (where there comes 3 enemy, or a warrior and a guy with a grapling hook demands at least a slvl 3 Summon Shadow and not a little luck, but can't deal with the end boss who just keep summoning minions).