I noticed that too. Could be because Abyssal rune has a 25% proc rate and Sundial 10%.

Looking at his recent activity, I'd assume that he reglyphed/respecced for ToGC anub. You'll also notice he specced 2/2 Gale Winds, which you would never take for single target DPS.

I figured that I would give a little information about languish...

It does stack, in terms of each additional cast resets the debuff with the additive total of the damage caused.

It ticks at 2 and 4 seconds, but, if you get the tick at 2 seconds then crit, the amount of damage added to your current spell is only half of the total ticking.

So, if you crit with starfire for about 15k(arbitrary number), you get an additional 1050 over the 4 seconds, ticking at 525 at the 2 and 4 mark. If you get a starfire crit before 2 seconds for the same amount, you now have 2100 over 4 seconds, but, if you get it after, the tick will deal 525 damage, and you will only have 1575 ticking over 4 seconds...so on and so forth.

There is also no separation between starfire and wrath, so I suppose you could get to large numbers if RNG had its way...for example, during lunar with hero/haste pots, you could probably squeeze 11-12 starfires into the phase. If you had omen of doom, critting for about 20k during, you would have 12 straight 1400 additions, 16,800 total damage, ticking for 8400 if you didn't crit afterwards. It seems pretty straightforward, and it pretty much equates to 7% increased critical strike damage on starfire and wrath.

EDIT:

Also, in regards to DoTs without IS glyph and 2T9, I would imagine that moonfire will still be worth casting between phases heading into lunar, but would likely be cut out heading into solar because its damage without the DoT critting with only the 5 ticks is roughly on par with insect swarm unglyphed. 6700(is) to about 7000(mf) without any debuffs. When moonfire is extended, it still generates a total of almost 11000 damage, which would almost certainly be worth it.

That being said, if there was a point where the DoTs were completely useless with the exception of accessibility during movement, it would call all glyphs into question...and in that regard, focus/starfall would be better choices with one other. I doubt we will ever get to that, though.

On top of what the poster above me said, you also forget that Zoomkins has such an insane amount of gear that he's well over crit cap, and can afford to lose the 3% crit that's gained from Improved Faerie Fire.