WoWS: Effectiveness of the Expert Marksman Skill

From Redditor tozim.
In his words:

As I was prepping to train up a new Russian cruiser captain, I sat there with 2 points, as I do many times, trying to figure out if it was worth it to take Expert Marksman for this line. Since this skill is based on a 2-tier flat increase instead of a percentage increase, it affects all ships differently. I decided to math out the EM bonus for the VMF cruisers, and as I was working on that I extended it to all the ships in the game.
Now, for BBs you might always want to take EM because nothing else even makes sense at level 2, but it gets more interesting for Cruisers and DDs as there are a few other skills that can give you more effectiveness at that level.
So below is the chart, I calculated both the absolute 180 degree turn time improvement, as well the percentage improvement that 2.5 or 0.7 degrees per second represents over the default traverse speed. The 180 degree turn time is how the speed is represented in-game, but for brawlers or knife-fighting ships, the % boost might be a better deciding factor for selecting EM.
All of the source data (180 degree turn time) from which I based my calculations came from the official Wiki.
Google Docs Link
EDIT 2015-02-15 10:20
Google Docs Link
– a few updates to the structure and ordering of the table based on feedback
– Kongo 180 Time changed from A Hull’s 64.29s to C Hull’s 54.5s
– Wyoming and Arkansas split because they have different 180 Times
– Gnevny and Gremy combined as they are are same class, same tree, same speed
– notes moved to a comment
EDIT 2015-02-16 08:36
– added Orlan