For a long time, Marksmanship has been the preferred specialization over Skirmishing in the suggested setup by [dT] and Snow Crow, and ditto on the wiki site Metabattle. It provides:
On the other hand, specialization in Skirmishing at its best could provides:
Say, we have a Soulbeast in full Ascended Berserker gear with S. Rune of Scholar, in Beastmode with Rock Gazelle.
If specialized in Marksmanship, this is what the expected damage would look like:
GS Damage = Power * [(77.86% * 180.33%) + 1] * 1.05 * 1.15 = 290.29%, assuming target is permanently movement-impaired/disabled. (I believe the assumption is practical?)
x/Axe Damage = Power * [(77.86% * 188.40%) + 1] * 1.05 * 1.15 = 297.79%, ditto.
(Build refenece: http://gw2skills.net/editor/?vNAQNAR3XnUqAVsgtCCm8Cs8il8A7pOsEyALBgCwpL/9ef7vl49EA-jhRBABmpEkS1fM+iKc1+jyP809AwTKgUARMZD-e)
If specialized in Skirmishing, then:
GS Damage = Power * [(92.62% * 197.00%) +1] = 282.46%; while 297.00% if constantly flanking.
x/Axe Damage = Power * [(92.62% * 205.06%) + 1] = 289.93%, while 305% ditto.
(Build reference: http://gw2skills.net/editor/?vNAQNAR3XnUqAVsgtCCm8Cs8ilCBj5d1uSd5X3vb59pLMDCAl49EA-jhRBABA8kCua/R5nxXUBKV/BPdPmpEkUARMZD-e)
The results seem rather close to me (2.7% ~ 2.8%; 2.3% ~ 2.4%). Bleeding with Sharpened Edges would also contribute, though I believe on a power build it would not suffice. The main factor to consider would be whether the flat ~4.76% critical chance increase with Spotter for your allies would make up for the difference. If it does, then it would not be a bad alternative if your group happens not to have a Druid for Spotter.
Also, for Fractals, there are potions, and for Raids, Banners and other factors must be taken into account, and perhaps one has to recalculate the entire whole thing. Just some preliminary crafting here.
Please do let me know if there is anything I failed to account for!