Chain & Sprocket wear

HHHH to my eyes your sprocket just looks like a classic case of worn cog from an old worn chain. There's a fair bit of 'sharks tooth' going on.

Probably, as the difference in wear between teeth is quite minimal. It's just that the uneven wear may mean the rear cog isn't spinning round properly, so it's worth checking the axle if your at it already. I've been running a Tomicog which isn't centered amongst the bolts evenly, the wear is definitely uneven. If the chainring weren't round, the point the chain is under tension varies across the cog depending on the ratio, much like skidpatches, so the wear isn't focused on one point with the ratio he's running. Wear would only be focused on a single point on the chainring, although this is slightly less of an issue. I'd still check it all though ;)