I agree Nodge - looks like part of the diagnosis. The intent pattern on the cylinder head really doesn't look too bad. Typically indents tend to be a little deeper on the exhaust side of the head - largely because this is the side that gets hottest (no cooling air fuel mixture on this side of the head!)

What is interesting - and perhaps I am seeing things that aren't there - is that the ring indent pattern seems more described on cylinders 2/3, extending to the inlet side. Perhaps this supports a localised over heating? Air lock in the cylinder head perhaps???

The fire rings contact area on all cylinders looks fine to me.
I'm sure you had an air lock that has caused localised heating of that part of the gasket. This would explain the discoloration and possible delamination of the elastomer seal.
Fitting another gasket should make the engine work again. However it wouldn't stop an air lock causing a repeat failure in another 2 years. I'd be checking out the coolant ways in the head, for any possible causes for the air lock.

OK - just a test