The Enigma Order

In theory. In practise it's not that bad.

Stolen from mmo-champ ( written by Yvaelle):
Math looks good, but I just eyeballed it 

Those numbers aren't mine actually, and if we're going to present them as you're showing, we should probably pull relative DPS for all specs for each gear level. All numbers taken from the official simcraft patchwerk sims linked below.

Normal:
http://simulationcraft.org/510/Raid_T14N.html

Heroic:
http://simulationcraft.org/510/Raid_T14H.html


Just so we have some scale factors to look at as well, here is Shadow scale factors in 509 BiS:
Int - 4.04
SP - 3.21
Hit/Spirit - 2.63
Crit - 1.72
Haste - 1.75
Mastery - 1.65


Arcane Scale Factors in 509 BiS:
Int - 5.09
SP - 4.13
Hit - 4.00
Crit - 2.09
Haste - 2.42
Mastery - 2.75


Affliction Scale Factors in 509 BiS:
Int - 4.96
SP - 3.98
Hit - 2.54
Crit - 2.08
Haste - 2.39
Mastery - 2.76

Comparing these to shadow in single target is basically comparing the best specs to the worst, since we're second bottom and arcane and affliction are the top - it gives a pretty good picture of how wide the scale factors actually are, and explains why Shadow's DPS is as low as it is. For the uninitiated, a scale factor is a multiplier of how much an increase in a stat increases your DPS, higher is therefore much better.

As we can see, an equal upgrade of Intellect results in a ~25% bigger gain in DPS for Arcane and Affliction than it does for Shadow, an equal Spellpower increase gives Arcane 28.66% more damage than the same increase for Shadow and 24% more Affliction. An upgrade of hit is worth 52% more for Arcane than for Shadow and Affliction. An upgrade of crit is worth 21.5% more for Arcane and Affliction than the same crit rating increase for Shadow. An upgrade of Haste is worth 38% more for Arcane and Affliction than it is for Shadow. An upgrade of Mastery is worth 67% more for Arcane and Affliction than the same mastery rating increase for Shadow.

Shadow is tied for last place of all DPS specs on Patchwerk, both in 496 gear and in 509 gear. This has been justified on the grounds that there are no Patchwerk encounters in the current tier. Since Shadow has an execute our damage goes up the longer / more often there are execute chances in an encounter. During fights with frequent adds or prolonged low health boss phases, Twist of Fate allows us to maintain a 66-90% uptime on a 15% damage buff on a number of fights this tier. In encounters where DoT cleaving is possible, SW:P and VT on secondary targets is a DPS bonus over our single target rotation (multi-DoTing), and many fights require a high amount of healing - where Shadow provides good utility (even though Support specs officially do not exist).

For reference, here are the other caster specs scale factors:

Balance Scale Factors in BiS 509 gear:
Int - 4.24
SP - 3.33
Hit - 3.86
Crit - 2.04
Haste - 1.61
Mastery - 1.91

Elemental Scale Factors in BiS 509 gear:
Int - 3.86
SP - 3.13
Hit - 3.94
Crit - 1.47
Haste - 1.27
Mastery - 1.59

Fire Mage Scale Factors in BiS 509 gear:
Int - 4.73
SP - 3.55
Hit - 4.10
Crit - 2.92
Haste - 2.27
Mastery - 2.30

Frost Mage Scale Factors in BiS 509 gear:
Int - 4.59
SP - 3.67
Hit - 6.23
Crit - 2.00
Haste - 2.09
Mastery - 1.92

Destruction Lock Scale Factors in BiS 509 gear:
Int - 4.28
SP - 3.39
Hit - 3.09
Crit - 1.94
Haste - 1.75
Mastery - 2.21

Demonology Lock Scale Factors in BiS 509 gear:
Int - 4.35
SP - 3.47
Hit - 3.07
Crit - 1.89
Haste - 1.51
Mastery - 1.86



TL;DR:
The concern about our single target damage isn't a worry about the possibility of fighting Patchwerk 3.0 - we are concerned that as our gear continues to benefit us less than it does our competitors, we will fall further and further behind. Since we started in last place, it's hard to demonstrate how far we slip without verbose numbers, for which I apologize.