I did some testing on amun.
passive conc5 from lb's, crit buff from sb's + 30conc buff from sb's + superior bow with +5conc + 5conc gloves = 125 conc 29.7% crit chance (18.2% without buffs)
And I can barely see difference between buffed and unbuffed amount of crits, + this setup is purely testing, never could use 19lbs+19sbs in war.
So IMO it's worthless to skill for crits like this
edit: well sometimes it seems to be about as it shows on char screen, but still dunno if 10-15% more crits is worth of tons of power points+buffing