I posted this in a thread or 2 now, but seems some people didn't read them.
You need to get the DPS by actually taking a stopwatch and a fixed amount of damage and then doing ther math yourself, Damage meters are NOT accurate if you are not constantly attacking the target.
In the case of the glyphed Imp there is such a long gap between volleys of firebolts that the damage meters just stop tracking for a bit in between, leading to grossly inflated DPS numbers.
Even inexpertly done, with the ingame stopwatch, clicking the buttons and all, you can easily see that when you take a fixed amount of damage, then time how long it took to get to that damage, then divide things that you get a much more reasonable amount of DPS out of the glyphed Imp then you do by looking at recount or skada or tinydps or whatever.
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I did some practical testing in dungeons and found three strategies to be the most workable
1) Grimoire of Supremacy: Fel Imp (glyphed)
2) Grimoire of Service: Imp (glyphed, baseline)+Felguard(Grimoire) [single target]
3) Grimoire of Service: Felguard (baseline)+Felguard(Grimoire) [AoE]
wrathguard just doesn't hack it for me.
Yeah, that's the pro way to do it. I don't normally have a need for logs in our raids, so I don't even have an account set up there or anything. My RL seems to know enough from basic skada info to adjust what we are doing, so I've never felt the need to go the extra mile and log what we are doing. I might start doing it in Mists, a point to consider at least.
From the info you got though I'm a bit surprised Imp is still doing so well, I guess the tiny bit he was in front on my own tests translates to some pretty substantial differences on a longer fight. I put it down to just variance and noise in my test results, and that longer, more even tests would translate to less differences between the pets. A point to look out for in balance patches on the horizon.
At the moment I wouldn't mind Imp actually, he's ranged so easier to target switch, Stam buff that my raid usually lacks unless we use the Inscription Scroll, and a minor heal that helps in a pinch. Using the glyph though would be a bit of a nuisance, pets should be balanced, and not get a DPS boost from it.
At lvl 90 and hit capped felguard does more than tthe imp for me and i use felguard becuz glyph of service is insane damage and my two felguards r doing a good amount of damage than the wrathguard on skada segments on mogo vault bosses and heroic bosses