Yeah it's my build.
I keep on using it cause it's the only build I can go far with and is easy to play.
My current character http://te4.org/characters/107887/tome/ab2f5ac1-78f6-44dd-bfff-ee16b343f083
The dude I used to unlock Marauder died on dreadfell a few turn after the unlock, and I didnt use the online archive at the time. But you can check some of my dead shadowblade (I have some at various level) to see how it goes for the build.
But basically you play without spending too much point till lvl 3. At 3 you can have illuminate raised to 4 and do 80 damage. You begin raising MAG and search for a staff to use.
When you have 100 gold you buy the Staff mastery in the mage town and spend your Cornac point in the tree.
At level 10 you unlock the stealth tree. And then every strike is a critical. So illuminate is around 200 damage. May be it's easier with stealth at lvl 5 and Staff Tree at lvl 10.
With the summertide vial (10%) a staff (15%) and a few +light damage item you can get around +40% on light. With fully upped Shadowstrike (+80%), and Lethality (+30%) your critical will do +260% damage. So on average you do 400 damage as soon as you see stuff (I automate Illuminate to fire as soon as enemies are visible - ! De-active the automation when doing escort, I killed some of them like that! -). Plus you blind mobs, so the game is a cake walk. Except you become reckless, and you're clueless with hard bosses.
And if mobs survive illuminate you have the channel staff (range 10, hit without accuracy, bypass armor). I actually (since lvl 20) can do 600+ damage with channel staff thanks to the 140% MAG ego , physical artifact staff "Big Knocker".
Then you just have to find a -100 light resist mob and you'll unlock the marauder without noticing.
I dont know if it's viable for the end game, but it make the early game very easy and fast (I think Illuminate has the better range of all spell/weapon, and you hit invisible/stealth mobs)