The new bowman tweeks on 1.2.327

No, that seems accurate. Adding a Critical ring can also bring it to a 70% critical rate.

Is the new +15% to minimum crit only on Bow Expert, or is it also on Marksman Boost?

Edit: With these new skill advantages, it is hard to decide what to max first; it no longer is either snipe or pierce, it is Snipe, Pierce, UltiStrafe, MMB,...