This is not exactly right, The interaction you are seeing is Hurricane procing from rupture or deadly poison. When it procs from another ability it creates it own Hurricane buff. Like wise you can see it refresh the MH and OH Hurricane procs. This is pretty easy to test with a target dummy. Shiv from the side so you don't get any auto attacks till you have 5 points then Rupture. Hurricane will proc of rupture ticks same as DP ticks. This is why you can have 3-4 Hurricane buffs up at once.

Best estimates at the moment is that LW will be the best profession for Assassination for at least the first couple tiers of content. Those estimates could yet change. And while there is reason to believe the same will hold true for the other trees, we really don't have any detailed numbers at this stage, so I'm hesitant to make any broad recommendations.

So we will be rolling with Leatherworking / Engineering?

Hard to say. The benefits of engineering are always hard to quantify due to heavy reliance on activated abilities and various nonDPS benefits. This is doubly true now, as I haven't had time to sort through the list of engineering widgets and figure out what people will actually be using (if someone would like to put together a list of the reasonable options for each slot, that would be a big help). But here's my best guess.

DPS, for assassination, in the first tier or two of content, will be heavily dependent on how much agility you can stack. There are other things at matter, but in terms of raw DPS increase, Agi appears to just win relative to the other stats. Hence, the value of the professions tend to correlate pretty well with how much Agi they give you. Alchemy, Blacksmithing, Enchanting, and Inscription all give 80 agi; JC gives 81. This is the baseline amount of benefit that a profession needs to give to be competitive.

Engineering does not appear to have any large agi boost of this form (or at least, I haven't found one). It provides numerous other smaller benefits which I haven't had time to catalog, but in terms of the sustained DPS value of the profession, the lack of a large Agi bonus is concerning. Hence, if I had to guess, my suspicion is that from a sustained DPS perspective, the value of engineering will not be competitive with JC or the 80-agi professions.

However, what must be remembered is that the benefits of engineering tend not to be focused on single-target DPS. Things like Rocket Boots may or may not provide a DPS benefit, but they provide significant utility (although how important that utility is in a world where sprint is on a 1 minute cooldown can be debated). So regardless of how they perform from a sustained DPS perspective, they may or may not prove to be worthwhile due to their contributions from a utility perspective. Hence, this is the way I'd characterize the professions at the moment, in terms of viability to Assassination PvE DPS for the first tier or two of raiding:

• Leatherworking is strong, and likely to be worth having as one of your two professions.
• In terms of raw stats, Jewelcrafting is second best, if barely.
• Alchemy, Blacksmithing, Enchanting, and Inscription are very competitive with JC. I would not recommend rerolling professions between these and JC or vice versa.
• The gathering professions - Herbalism, Skinning, and Mining - are, respectively, bad, worse, and awful. If you intend to raid in a serious way I do not recommend these professions.
• We need proc rate testing/information on Tailoring before we can say *anything* about how viable it is.
• Engineering is unlikely to be worth it from a pure single-target DPS standpoint though I don't have enough information to speak with any certainty. The extra utility it gives may or may not be enough to offset this.

In short: assuming current modeling is correct, you will probably want LW as one of your professions for the start of level 85 raiding. More information must be gathered and more information accumulated before we can comment whether the best "second" profession is Engineering, Tailoring, or JC - and even then, it might be to some extent a matter of opinion. The only thing I feel confident in saying with any certainty at this stage is that the gathering professions are likely to be weak from a PvE raiding perspective.

Wont the Alchemist only potion (Flask of Enhancement) overwrite itself with the general flask (Flask of the Winds) ?

If yes this would make alchemy completely useless.
Or I am missing some mayor point.

You're missing Mixology. Alchemy will give the same sort of extra agility from Flask of Winds as the other professions get from things like Blacksmith sockets.

I figured cogwheels only existed to add a degree of customization to engineer crafted goggles.

My understanding of cogwheels is that they basically let you get your crafted engineering helm with your choice of secondary stats. If you look at the base helms (say Agile Bio-Optic Killshades), it has Agi and Sta on it, but instead of secondary stats you get 2 cogwheel sockets. If you compare this to a nonengineering helm of comparable ilvl (Wind Dancer's Helmet or Membrane of C'thun), you find that the stat budget is almost identical. Hence, Engineering helms + cogwheels are basically ilvl-appopriate gear that happens to always be itemized as well as possible. Which is nice. But the advantage also goes away the instant you get a higher ilvl helm, so as soon as you have access to heroic dungeon loot the advantage of the engineering helms evaporates.

Edit: Or what Feist said.

Re: Flasks. Mixology means that, with a conventional flask up, you gain the same bonus to stats that you would from Enchanting ring enchants or the two extra sockets from Blacksmithing. However, you don't always have a flask up, so they give you Flask of Enhancement to use the rest of the time - it's infinitely reusable and works in arena PvP and so on such that the functional benefit winds up being identical to the other, passive, professions.

They will probably add agil and str clickables to match the int one, it's strange that they didn't, but engineering strikes me as unfinished in that regard. Maybe the int is a typo though and they meant to use haste on the synapse springs though.

My question is how much better LW is as a profession.

Using the current EP weights, it's 130 agi (364) vs 65 haste (143) for assassination for a difference of 221 EP, equiv to 78.9 agi.
For combat it goes 374.4 EP vs 146.25 EP for a difference of 228.15 EP, equiv to 79.22 agi

So the EP of agi is gonna rise (relative to haste) so much to make LW significantly better?

The rating to percent conversions are dropping by a factor of 4 from 80 to 85, and average weapon damage (including AP) is only roughly doubling; hence the EP value of rating stats is likely to drop by roughly half, while AP and Str maintain their value and Agi only drops slightly (as the 2.2+ AP you get per point sticks around, and while only the crit component is devalued), making Agi/AP by far the most valuable stats.

To put that into specifics: what we've been finding for assassination is that Agi winds up with an EP value around 2.5, after which your second best stat is hit below the yellow hit cap at around 1.5 for entry raid gear. And the value of the other rating stats only go down from there - right now it looks completely possible that haste and mastery will be the best uncapped rating stats for Assassination... with EP values right around 1 for BIS pre-raid gear, climbing to 1.2 or so by the end of T11.

Edit: To make that perfectly explicit: yes, it appears Agi may easily be worth twice as much as any uncapped rating stat for entry raiding. 65 haste is thus only about as valuable as 30 agi according to current estimates, meaning the LW bracer enchant is a 100 agi upgrade vs 80 for other professions.

Edit 2: Please note the vast number of qualifiers on the statements in my last few posts. These are current estimates. We are still working on the model(s). These numbers may yet change. I'm giving you our best estimate, but our estimate still has significant room for improvement. So be careful not to read too much into the numbers at this stage.