tried her in a bot game on the PBE before it went down, and they really did a good job with the update.
each of the 5 attacks on her "focused" Q does 0.23-0.27 AD (times the crit passive) per attack, so each runaan's bolt apparently does half that + 10 I guess. when I had just BF + runaan's she felt pretty similar to Kalista in terms of power with the same items. it was too hard tell whether the BotRK applied on the runaan's hits, but I assume that if it does it's something they'll fix later.
her passive slow is probably way too strong right now and might lowered. just her passive slow scaling is about on the same level her old Q was on it's own (5% compared to 15% at level 2, 23/20 at level 10, 29/35 at level 13 and 35 at level 16) but the active on her Q increases the slow by 20%. with the Phage passive being on Black Cleaver, she can kite better than ever, perfect in the new tank meta.
I'd be really interested at seeing how efficient PD/Shiv will be on her thanks to the crit changes. Runaan's/BotRK might be too good to pass up, and I could honestly see building only IE for crit being a legitimately efficient option.
more importantly, it her new Q made her actually ~fun~