Crosby's results are inconsistent. His results are stellar through 2010, and surprisingly bad after. I know that part of it is due to Malkin being a big part of the "R-Off" calculation, so he faces a similar problem as Messier and Lidstrom. But his performance in 2016 was disappointing (especially for a Smythe winner) - for all the talk of Crosby being a great two-way player, the Penguins were actually outscored at ES while he was on the ice, despite being a very strong club while #87 was on the bench. Crosby actually has a negative cumulative R-ON from 2010 to 2017, on a team that's been solidly positive over those years.
I think Crosby's numbers actually show the potential limitations of this analysis for a single postseason. We have advanced stats for the 2016 playoffs, so we really don't need to use a goals-only analysis, and Crosby's 5-on-5 on-ice numbers were actually very strong (source:
Natural Stat Trick, so obviously using their definitions of scoring chances and high danger chances):
With Sidney Crosby on the ice in the 2016 playoffs (5-on-5):
Shots: 220 for, 159 against (58%)
Scoring chances: 216 for, 162 against (57%)
High danger chances: 85 for, 67 against (56%)
The problem was that his percentages were terrible:
On-ice shooting percentage: 7.27%
On-ice save percentage: .887
Goals: 16 for, 18 against (47%)
A full playoff season for a top line forward is still only about 400 or so total on-ice shots, and the normal variance on that can be insane, even between players on the same team. In the past three playoffs combined at 5-on-5, for example, Pittsburgh's save percentage is .899 with Crosby on the ice and .949 with Phil Kessel on the ice. The result is that Kessel is +18 at 5-on-5 compared to +10 for Crosby, even though Sid has 39 points at 5-on-5 compared to just 23 for Phil during that period (and despite Crosby having a better shot share, scoring chance share and high danger chance share as well).
Similar things likely happened to other elite players throughout history during specific playoff seasons, so I wouldn't be at all confident saying that a good or bad on-ice ratio necessarily reflects a player's actual two-way performance for a single playoffs, or even a couple of playoff seasons in a row. I think you need something on the order of at least 3-4 full regular seasons before you even start to get into something approaching an acceptable sample size for on-ice/off-ice goals numbers.
We all know what happened with Ovechkin. For years he was labelled a choker and a loser. Then he had a career-defining playoff run - the type he was always capable of having - and suddenly half of the main board is calling him a top ten player all-time. As you can seem I don't have the data for 2018. I know it was a very good run, but I can't tell you if it was historical or merely very good. Aside from that, Ovechkin had one extremely strong performance in 2009 (this was during his "Bobby Hull phase", and then three disappointments (thus was during his "Brett Hull phase"). It's a tale of two careers here. Ovechkin was stellar through 2010, then generally bad afterwards.
I don't think this is necessarily all that meaningful, but here are Ovi's 2018 playoff numbers for completeness' sake I guess (using the same method as for the others):
Ovechkin was on for 44 total GF, 16 total GA, 21 PPGF, 1 PPGA.
Washington was +63/-42 at even strength, with 1 SHGF and 1 SHGA.
After accounting for shorthanded goals, Ovechkin would get credit for +23/-14 at even strength.
Which gives: 1.64 on-ice, 1.43 off-ice
Pulling his 5-on-5 numbers only from the 2018 playoffs, Ovechkin had a 53% shot share, 54% scoring chance share, 55% high danger chances share, and 66% goal share (because he ran hot with a 10.9% on-ice shooting percentage and .935 on-ice save percentage), to go with his 15 even strength points, which is still all in all a decently impressive playoff run.