@ Shifft
You dont need to lose Vitality...
You can spec 16/45, but you will lose Imp Evis (well, who uses evis? I like rupture a LOT better, much more consistent damage.. I hate when I see a 1400dmg non-crit evis

.. while Rupture ticks for ~300 x 8 = 2400dmg.. every single time.)
I tested on the PTR like below (assassination tree):
5/5 Malice
3/3 Ruthlessness
2/2 Murder
5/5 Lethality
1/1 Relentless strikes
45 points on combat.. just the usual non-riposte build, xcept with 5/5 fist and 5/5 swords
Cheers \o/