I did few tests as pure PvE build for dest to see how rotation goes [with Emp Imp SFs etc, Btw did 32k conflagrate:P] and whats the distribution of damage between spells.
Incinerate 33,5%
Conflagrate 27,1%
Immolate DOT 15,4%
Burning Embers DOT 6,8%
Chaos Bolt 6,8%
Soul Fire 6,1%
Immolate DD 2,7%
Shadowbolt 1,7%
Above made up 87,9% of my DPS, Imp's Firebolt [direct damage component alone] did 12,1% of my DPS, DPS - 10k [pvp gear GS 5800].
So far it looks like THE glyphs for PvE destro are: Immolate, Conflagrate, Incinerate as these contribute the most to the dmg. Immolate's DOT alone does LESS then IMP does which some would say its better to glyph imp, but Immolate DOT makes Conflagrate a lot stronger and conflag is huge part of our dps. Incinerates 5% is rather obvious choice.
This id dmg shown by recount, but there's also damage done by imp.
glyphs: Immolate, Conflagrate [-2sec kicks ass], I couldnt find anyone who could do for me Glyph of Imp [+20% firebolt dmg which does around 1166 dps for me [DD part] and thus glyph would give an increase by ~233 dps]
EDIT:
Madness??
THIS...IS...BETA!!!
EDIT2:
Ive counted some things before sleep.
Player does 87,9% of total DPS, imp [just firebolt] does 12,1% of total DPS.
Out of that 87,9% player's dmg comes mostly from incinerate 33,5% conflagrate 27,1% and immolate DOT 15,4%.
To compare these to the imp we would have to count how big part they are of total dps [player + imp]
Thus:
incinerate 33,5*87,9/100 = 29,45% of total dps
conflagrate 27,1*87,9/100 = 23,82% of total dps
immolate DOT 15,4*87,9/100 = 13,54% of total dps
Thus the top 3 of spells that contributed to my total DPS are all better then imp and thus with what glyphs for them and for the imp do it is obvious immolate, conflagrate and incinerate are THE glyphs.
In this case as ive said i used conflag and immo glyphs thus i have results a bit higher then unglyphed, but with the synergy between immo + conflag [superb tbh] its no secret its better then imp glyph. Also incinerate was without glyph.
btw i didnt have improved soulfire as it seems bugged atm and didnt increase my haste at all.
On a side note i literally LOVE the fact tht if i have 30% crit, then my imp also has 30% crit, and he benefits also from 100% of my haste.
Kinda sucks imp and pets dont benefit from mastery [aside from felguard really when demo specced and demo spec in general]
mastery giving +20% fire dmg would actually make imp a lot more potent.