To clarify even further, you need 42.5% WITH the t19 2 set... without it you still need 50% base crit for 100% crit on holy shock.
The supposed breakpoint you should aim for is 42.5% but that's without nerving your mastery/vers too badly.
Right now I am sitting at 36% crit 33% mastery and 10% vers... with
this spreadsheet
it put's my average output at about 234k which was higher then stacking all crit gear. By roughly about 2-3k. Honestly that spreadsheet is wonderful and found me a great min/maxing option for gear.
Don't be fooled thinking speccing ALL crit is the way to go, not just yet.