Its all fixed... :\
I tried to overpower myself with stam/ag/dodge/dmg but nothing works...
However, i found sth as a rogue to make Garrotte work whenever you want (= you dont have to be in stealth!!), and same with cheap shot!
Just change a normal attack spell, like ghostly strike to garrotte or CS, and when - out of stealth - you use "ghostly strike", it will do garrotte/CS.
About CS: the stun will only work a few times, but then it has no effect anymore on the target, except that it gives you 2 combo points.
* I couldnt make ambush work out of stealth... :S
This wont make you take out illidan on your own, but it will let a significant DoT on your target PLUZZZ the 3 secs silence!
Also, you could use this tric on mounts (riding/flying) to use then when and WHERE you want! -> Flying above azeroth? Or maybe in Zul'Aman...

Its a bit more complicated since you use the *spell* related to the item, but not the item itself!
Hope you find some use in this...