Depending upon you level 90 tier talent choice your opener is going to vary significantly.
With Prime Elementalist, No Hero at Start:
-1s: LvB Precast
1s: Ascendance Macro- Throw whatever non-GCD ability you want in it, end with /cast Fire Elelmental Totem.
Usually, I pair Elemental Mastery with Prime Elementalist and Engineering Gloves, so macro this in as well. Also, this macro has the benefit of grouping the majority of your CDs syncing them and making them all available at the 6 minute interval, with minutes 5-6 available for putting another Fire Ele down and heroism- tracking Int procs and haste procs, and saving your second potion can set up maximum fire ele dps going into minute 6, generally where you will heroism.
Since Int potion lasts 25 seconds, ideally wait until 5:50 onward to use such that it is still active for Ascendance at minute 6. If you're forced to hero at 5:30, you'll still have hero for ascendance but it will not buff your fire ele, (however another heroism class may cast it again for you.)
If you still havn't heroed by minute 6, say 'fuck the police' and hit hero anyways, paired with your potion and fire elemental.
2-3s: LvB spam (usually will have an LvB proc, no dps "loss"
This opener is still a dps gain, and extremely strong burst, and with the 'late' cast of Fire Ele, you should see an even bigger increase in Fire Ele damage from any Int procs, your prepot and haste procs (why Ele Mastery is essential in high Mastery builds... the irony). This talent choice is strongest where you expect continuous Fire Ele up-time, and Fire Ele is not glyphed.
**I would recommend this build for you OP. In your case, this build is even 'safe' even if you did want to heroism at the start since you lack the legendary meta gem. Just remember to keep Elemental mastery on CD... if you find yourself forgetting to use it, try macroing it into something spammy like lightning bolt.
Other DPS points to keep in mind:
Flame Shock / Earth Shock- Remember to always have FS up. When you refresh it, make sure to only refresh it when there is less than 3 seconds remaining. Getting a timer addon is helpful in tracking uptime durations remaining. Timers are rather essential for the reason of keeping your shock cooldown clean. The thing to remember with Shocks, is that they share a CD. Therefore, if you have anywhere between 3 and 6 lightning shield charges on your ES, with 6-8 seconds remaining on your FS, it's a dps increase on long fights to cast ES before 7 charges.
Clearcasting buff: After any critical strike you gain the Clearcasting Buff, which will increase the damage of your next two spells 10%. Since LvB is a guaranteed crit, comboing a 7 stack ES to follow a hardcast spell, given you have the buff, or typically LvB (guaranteed crit)> LB hardcast, (for the first LvB travel time to hit)>ES. If you do get an LvB proc after your first LvB, arguably you should cast it, or combo it after your LB hardcast before ES. This will simply extend your clearcasting chain and will not occlude a chance to gain another proc of LvB. Usually just following the priority of spells is enough for this to take care of itself. However being aware of how you "space" your ES after critting can yield a better ES average, and a slight dps increase.
When Hero-ing on pull you should still precast... in the raid environment, it is sometimes optimal to hero 1-5s into the pull, macroed with Stormlash, if you're the one popping it. That being said, you can always hero pre-pull 1s, or on 0 if you have heavy dot casters with the advantage of precasting and dot openers.
In terms of Dpt you absolutely should consider burning your first LvB as a precast (even with EB) since it is better Dpt than LB, and EB buff you will need to preface Ascendance.
FS is second priority Dpt, especially in the instance of the opener, whereas LvB has a flight time, following with FS allows both to hit simultaneously at t:0. An immediate FS has the benefit of providing an early LvB proc, which helps maximize the number of LvB during Ascendance.
Even in the case of UF as a level 90 talent, FS is still priority, since its DpT is both higher and allows 1 additional tick, which can very well proc LvB, whereas UF does not. Casting FS after UF also causes a 1 GCD loss for the UF buff.
In the case where UE is used to proc the meta gems at the start, UE should still not precede FS for reasons mentioned above. The meta is just as likely to proc from the combination of LvB>FS>Ascendance LvB, even if it is guaranteed to proc from UE. Between the fact that the gem is likely to proc on a normal opener, and the fact that it is possibly to proc LvB pre-Ascendance, UE is therefore not always a dps increase, and shouldn't be recommended.
Also the "fact" that more haste gives more LvB procs through FS is a fallacy. While you may experience more procs, even if you had a proc for all 15 seconds of ascendance, the effective dps is the same as the person who casts through ascendance with 1s GCDs. Both cast 15 LvB over the duration because THE GCD IS ONE SECOND. Getting more procs does not = more dps in the instance of Ascendance and the opening sequence. The effect these procs play later in the rotation outside of ascendance MAY be of very minor significance and depends entirely upon stat weights. For example, the ele sham that is mastery stacked instead of haste stacked is likely to gain 2.5 + 1.75 damage per proc, whereas the haste build is not, even if casting at 1 GCDs, you might get double the procs and therefore double the damage. The thing is, is that there is no haste build that reaches 1s gcd all the time, nor is there one without mastery. Nor is there a mastery build without haste. Therefore the frequency of the proc rate scales in proportion of mastery RNG always. Basically haste can attempt to control proc frequency, but as mastery becomes larger as it has in SoO, haste becomes less likely to have a marginal advantage against mastery averaged over the fight duration.
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Also, I always precast in raid because I'm selfish. And because boss health pools in MoP are so high, the likelihood of missing a kill by 18k or so dps in 10 man is so rediculously slim that TBH I'm not going to sacrifice a GCD which does more damage anyways, (even if it did somehow happen...?) In 10 man the average DpT of any of my abilities except LB is enough to make up for the average 200k total Stormlash normal hit with 5 dps.
Otherwise Stormlash whenever the hell you want to.
WHAT? How is it wasting a gcd you're gaining 600k damage from one gcd, and unless you get PERFECT EoTE procs that one gcd actually nets you more dps than pre-casting, where you cut 1-2 seconds off of stormlash, that isn't counting you Fire Eles stormlash damage. By your definition of wasting a CD we should never use our searing totem because it's a dps loss because it doesn't hit hard. Using stormlash right before your ascendance would be optimal, not before you pull.
Also, it's very clear you're selfish in a raiding environment and I would hate to have you on my roster.
Why you're comparing this to Searing Totem, I have no idea. The DpT of Searing is such that it does more damage than one LB, since that is where it falls into priority. The same applies to Stormlash.
Anyways, that's my take on it, that's my advice. It's up to you to take that information and do whatever the FUCK you wanna do. I'll side with Endus and DpT > All.
Anyways, stacking Stormlash with Ascendance it so happens does have a major effect on overall personal Stormlash damage. So I stand corrected. After testing I ended up getting far more Stormlash crits... so given the marginal increase of even one additional Stormlash crit, Stormlash priority should be with or as near to Ascendance as possible.
And yes, Endus always favors DpT, and is Ele sham god.
Honestly though I'd love to have his take on it.
A pull on Garrosh HC(latest fight I can refer to) would look like this.
Fully buffed, 300 well fed, flask 1k int,
Profs: Engineering, Inscr.
2-3 sec left to pull Fire Elemental ( which is glyphed by the time to try the aoe ) Will prolly go for UF further on(other opening then).
2 sec left Prepot
2 sec left Cast LB
0-1 sec FS
(Unleash Elements would come here if I use that talent)
0 sec Stormlash
Ascendance, Berserking(Troll racial), Engineering gloves = All in one
LvBs until adds reaches Garrosh
Lava beam and the rest is another story.
I hope I didnt miss anything.
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