A good deal of that fact is due to some early misconceptions of poison hit mechanisms, where we'd go for 7.5% hit and 7.5% expertise to cap spell hit, which isn't needed for poisons.

Subtlety rogues get energy from Slice and Dice via Energetic Recovery.

Energetic Recovery - Spell - World of Warcraft

Nevermind, in the parse, he's clearly playing assassination.

The rogue in question was Assassination for the parse, though. Considering it shows up the same way though, I'm going to guess it's some sort of exploit. Maybe starting out as Sub and getting SnD going before switching to Assassination? Possibly the "Sub" version of SnD stays on you?

Subtlety gets 8 energy per SnD tick, not 5 energy, according to both the tooltip and a few subtlety parses I checked.

Looking at that same rogue's other kills that night, he only seems to be getting the 5 extra energy from SnD on that one encounter. No other rogues in the top 100 or so are showing that energy gain. There's definitely something strange going on with this particular encounter on the parse.

I tried swapping specs on both live and the PTR, and as soon as I swapped, my SnD buff from subtlety disappeared. Unless there's some other trick, I'm not sure what's going on.

I just tested the 2 Piece Tier 6 Bonus and it is bugged:
In addition to the 5% Haste bonus (which disappears after changing the Set), it provides the extra Energy you can see in the Log.
In order to this:
- Redirect a few Combo Points from the Trash to the boss (only possible for the first two bosses in Mogu'shan Vaults)
- Equip two Tier 6 pieces
- Use Slice and Dice
- Equip your normal gear
- Refresh Slice and Dice with Envenom before it expires.

Even though I haven't checked with him yet, I'm fairly certain that Grufstandor has indeed used Slayer set bonus to get the extra energy. I've never quite used it before myself, but a rogue that raided with us in Dragon Soul told me he found out about that bug, and I believe he used it from time to time, as he played combat. I completely forgot about it back then, enjoying subtlety and not caring much, but I assume it will be fixed soon - and it should.

humm tried it in hof but the t6 haste bonus went away perhaps 3 seconds after bosses engaged

You lose the 5% haste when you change sets but you still gain an extra 5 Energy per sec which puts the Energy Regen almost on par with combat. I've tried farming with this works quite well but yea as someone's said not really worth using it in raids in case there is a chance Blizzard ban people using this. It isn't exactly "game breaking" but yea other people see it differently.

Small Edit: I believe you can only use it on roughly 3-6 bosses by my count.

Stone Guard, Feng in MSV.
Possibly Vizier (not 100% takes a few seconds for him to become active after the last group is killed), Amber Shaper in HoF and maybe Empress although takes a while for her to appear.
Possibly Council (again not 100% sure takes a few seconds after the last group is killed to become active) in Terrace.

Rest of the other bosses either have no trash before or they have a long period in which they become active.

You can use it on Stone Guard, Feng, Gara'jal, Zor'lok, Ta'yak, Garalon, Un'sok, Shekzeer and PotE.

Other for ranking purposes though, it is obviously rather useless, as you can redirect from trashs only once. Would have been possible to take advantage of it when you could attack the Puntable Marmot, before 5.1, but as far as I know, there is no more attackable item that can be used in raids.

These EP values are just rouge gesses, but here you go:

T15 2pc EP values:
Combat: 350
Assassination: 850
Sub: 900

T15 4pc EP values:
Combat: 1600
Assassination: 950
Sub: 1200

For comparison T14 2pc EP values:
Combat: 1600
Assassination: 1300
Sub: 1200

For comparison T14 4pc EP values:
Combat: 2600
Assassination: 1200
Sub: 1700

So it would seem that our corrent set bonuses would be better. If someon has other numbers please do share