Sure with raid buffs breaking thats a peice of pee. This wasn't taking into account raid buffs though and was based purely on wrath spam.

Except when natures grace procs at a certain point wrath is always greater dps than starfire, because it basically gives 126% of the damage component (compared to 120%) in the same time interval. Mana concerns can make this impractical though (but thats what downranking is for )

Wrath spam definitely "feels" faster on an NG proc, but it's only because the casting time of the next spell is shorter. As Boevis said, gcd is still 1.5 seconds.
Wrath casting time is 1.5 seconds, after an NG it's 1 second.
So after a crit, you have to wait for 0.5 second before you can cast the next spell no matter what you do. Ideally, the best thing to do is to cast a starfire as soon as you get a crit, as you wouldn't face this problem. Pretty much any effect that shortens the duration of a 1.5 second cast spell is useless.
This is one of the reasons I focus more on pure +dmg before +crit. Usually in a raid I'm put in a group with a shammy. On any boss fight, when he uses heroism near the end of the fight, I've found that starfire spam is a better idea as you totally circumvent any gcd problems.
Wrath spam seems to work well on shorter fights like in kara. But again, highly inefficient casting cycles are possible in shorter fights - mf+is+wrath spam. With raid buffs and around 970 +dmg it's pretty easy to break 1k dps in such situations. Wrath spam alone is around 970 dps fully raid buffed.

Mana is still a huge issue for moonkin on some of the longer fights, and starfire is pathetic in the base damage it does compared to other spells in the game. Wrath is extremely mana inefficient dps and moonfire is a joke. So we have basically 1 almost insignificant dot (swarm) and a woefully inadequate spell - starfire that has less base dmg/casting time than any other spell in the game.
Our aura is a complete joke. 5% crit is like give or take 15+dmg x5 ~ 75+dmg.
All shamans get a base 101+dmg wrath of air totem. The utility of a moonkin is starting to fall far behind other more potent offspec casters like shadow priests and elemental shamans and is slowly going back to the sad oomkin joke status.

Insect Swarm and iFF are actually pretty amazing. IS is still 2% Boss miss and extremely mana efficient, and iFF is going to be ~2% more DPS direct to melee, and a good 3% more DPS from anyone who is bound by threat since the MT is using all of that hit.

Overall yes, it's rather pathetic. Starfire and Wrath didn't scale up like they should have. Having our spells be equal to an untalented mage/warlock is rather pathetic when moonkin utility is still very low.

Your paladin healer loves you for it.

The aura is good theres no point questioning that, but the raid-slot to get it isn't generally worth it in returns of damage.

Sorry I guess I wasn't clear. What I meant was that 1% crit is roughly around 15 spell damage for a typical dps caster with talents like ruin/ice shards/elemental fury/vengeance etc. It's a very ballpark figure and I'm making a lot of assumptions like the caster has around 800-1000 +dmg and has the appropriate talents.
So 5% crit is worth around 15x5=75 +dmg.
Now of course there is some variation, but this is a good ballpark figure to work from.
Wrath of air is a base shaman ability that's 101 +dmg. Another thing to notice is that having crit may lead to damage spikes, and threat issues, whereas a flat +dmg boost is safer.

Not exactly a fair comparison. A talented frostbolt gets 71.4% of damage gear and 81.4% untalented. (10% nerf)

As someone once put it, it basically comes down on how deliver the +dmg warhead.

For instance both the spells you mentioned start to become similar in dps at around 1000 +dmg. (starfire 529 dps frost 547 dps) At 1400 in +dmg they are basically the same with starfire coming out 1 dps ahead.

Granted it is just rough math, but you have to consider the whole +dmg warhead thing.

Lets talk about this for a moment.

One way to model it for starfire would be: Damage / (3.5 - (.1 * Starlight Wrath) - (.5 * crit%)) for just using starfire.

As far as cycles go, IS-SFx3-Wrath is probably the best sustainable cycle, replacing the Wrath with another SF when Grace procs. Model this by multiplying the damage of each cycle by the chance for it to occur. Keep in mind the SFx4 requires 3 NG procs to be 12 seconds, if only 2 procs occurs it becomes a 12.5 "extended" second cycle. 4 Procs is extremely rare, but you're still best off waiting the .5 seconds to start the next cycle instead of trying to fit a wrath in there. And with only 1 proc you're better off casting wrath instead of extending the cycle by a full second.

(ISdmg + (SFdmg * 3) + Wrathdmg)/12 * ((1-crit)^4 + ((1-crit)^3 * crit) +
(ISdmg + (SFdmg * 4))/12.5 * ((1-crit)^2 * crit^2) +
(ISdmg + (SFdmg * 4))/12 * ((1-crit) * crit^3 + crit^4)

Feel free to correct my math there, I know it's longer than necessary.

Does insect swarm stack with scorpid sting?

If it doesn't, does it still do enough damage of its own to warrant using?