Shadow Blades reduce the cost of all abilities by 40%
Does this mean adrenaline rush for assassination?
Does this mean AR is not good to use with SB for combat as you'll have too much energy?
Shadow Blades is still best used during Adrenaline Rush, because it buffs your auto attack damage while also giving you additional combo points for more eviscerates. It's just a bad set-bonus for Combat.
Good burst of damage overall.
Faster playstyle - more spamming; for assassination it's a sensible thing, for combat it could lead to energy capping due to the use of AR + SB over an increase of haste. Not completely sure if it's a risk for sub too, but it doesn't seem the case.
Dps increase? Check. Not a good mechanic anyway - it's a replica of the TotT set bonus, just with a longer CD and a bigger effect.
I'll close this as we're going to see some thread proliferation around changes and new information coming up.