You do realize this is just merging the old SS glyph with the skill itself? We used to have a glyph on the MoP PTR that increased dmg by 25% and energy cost by 25% which is EXACTLY what this change is, and the Ruthlessness thing is so far from new I just want to cry, it's been out since bloody Vanilla dammit!
As Pathal point out, this will have a MASSIVE ripple-effect, SS is what, 8-10% of our dmg? They will buff that by about 2-3% at the cost of reducing the dmg from all our finishers due to less CP's and pretty much any CP using ability INCLUDING Relentless Blades reducing the CD's less due to a lack of CP's....
(also, the 10% Evis nerf, although unless it was reverted, also gave it a 13% higher AP scaling buff so not sure if that will actually be a buff or nerf in the end)
While in theory, getting 1 CP after every 5CP finishers sounds nice, but there are times we don't use a 5 CP finisher (say, SnD running out, only got 2 CP and low energy or transition, add dying or God knows)
And also as someone else pointed out, will this even work with Anticipation? The game is so sluggish with Anticipation (the amount of CP's or energy I've wasted waiting for my Anticipation charges to be added so I can use another finisher during CD's.....wow)
And as others also point out, this will make leveling a Combat Rogue really tedious work, or even playing Combat on any level excluding the really high-end geared ones with insane haste levels horrible.
This is just my 2cents
(Btw, trying to go along the lines of "wasting CP's during CD's or w/e kind of stuff is pointless, everyone's done it a ton due to how server-dependant we are during CD's)