I don't see the reason to go 31p concealment anymore, 12s backstab cd? All you get from 31p is acid blade, a bit of additional damage, 30% crit damage(12s cd, remember?), 1,5s knockdown.
23-16-2 ftw. The buffs to the Medicine tree are superb, 3k+ crits from probe, 3 TA's, duration of TA's increased, awesome awesome.