Guild Wars 2

Hey, I need a little help on a choice. First of all this a build for WvWvW and I will only WvWvW with it.
At the moment I run with this build : http://gw2buildcraft.com/calculator/thief/?7.3|8.1c.h1.a.1c.h17|5.1c.h4|1c.7m.1n.7m.1c.7m.1c.7m.1c.7m.1c.7m|21j.0.1n.64.1n.64.1n.61.1n.61.1c.61|a3.u36c.f4.0.f5|3l.1|57.5b.5a.5c.5v|e

And I would want to switch on a different build sacrifying some of my survavibility to achieve 50% crit chance and have more critical damage (roaming build mainly)

I came up with this setup : http://gw2buildcraft.com/calculator/thief/?7.0|8.1c.h1.a.1c.h17|5.1c.h4|1c.7m.1n.7m.1c.7m.1c.7m.1c.7m.1c.a1|21j.0.21k.d1e.31k.0.1g.61.1g.64.1g.64|a3.u36b.f4.0.f4|39.1|0.0.0.0.0|e

I dunno if hidden killer is still obligatory if you only have 50% (let’s say 57-60%% if I hit from behing)
Anyway let me know what you think guys and what could I improve.

Thank you

Anybody could give me some hints please ? :o