Bent derailleur hangar?

a spare hanger is a sensible thing to have sat in your toolbox- and a good thing to take with you if you go travelling anywhere with your bike. They're deliberately easy to deform/break and generally pretty easy to replace.

I think it does look in line, but the rear of the dropout/hangar are in different planes, which doesn't help - the hangar itself doesn't look bent. But your lbs should have an alignment tool to check (tho iirc there's a trick using another wheel if it has a threaded axle).
As suggested, a spare mech hanger is always a good idea - mine fits in my Rema p*ncture retpair kit box together with spare Sram chain links.

Actually, the cyclus tool is about 25 quid inc postage from Rosebikes - I bought one some yesrs ago, seem pretty solid
http://www.rosebikes.co.uk/article/cyclus-control-gauge-for-derailleur-h...

It looks to me like the hanger is thicker where the axle goes through it, and it's not significantly out of alignment to my eye. The way to check is with an alignment gauge which every bike shop has. Your photo IMAG0153 shows the pulleys and the cog are in a relatively straight line to my eye.

Looks like from the picture your hanger is not aligned.

Even if you buy a new one it might still need some kind of alignment to get perfect shifting especially for 11 gears these days.

I do mine and it is very easy and very rewarding to do and best of all you know you will get perfect shifting.

If in doubt get a new one and keep this one as a back up, so if the worse happens you have a temporary if wonky backup so you are not off the road waiting to get it fixed.

http://gearmechhanger.com/

just make sure you check which one you need for your model.

Go get a hanger alignment tool and align it.

Or take it to a mechanic. You can't tell if hanger is perfectly aligned or not from a picture.

Stupid question - is the wheel seated in the dropouts properly?

They can be bent back into shape, either with a long allen key in the mech mounting bolt, or if you're feeling flash (Or can borrow one as they're pricey.) a hanger alignment tool.
The axis of the mech bolt is meant to be parallel to the axel.

Best bet is to take it off the bike, quite a quick job ( at most 15 min to detach and put back.) and lay it on a table you'll soon see if its bent. I had mine bent after someone drove into the side of me and when it was on the bike I too was humming and harring about whether or not it was bent, when I took it off I soon found out it was as there was clean air under neath it. Ordered a new one off the net, quick fit and gears changing back to how they should be.

Have you fallen and hit the derailleur. ? From the angle it looks like the derailleur is slightly out of line with the cass. Does it track with this mis alignment over the whole cass? Hangers are cheap £10-15