I just don't think it's the airtight proof of dark matter Dr. Carroll considers it, because I don't think dark matter's the only, or necessarily the simplest, possible explanation.

I don't see a reason to think the normal matter emitting the X-rays didn't collide with the galaxy through which it passed. It seems likely to be the highest energy (hence it emits X-rays instead of visible light) so it should logically penetrate farther than the other matter native to its cluster, particularly if it's also the central and therefore densest part of that cluster, which appears to be the case (unless of course dark matter is present, in which case that part is the densest).

As for the lensing itself, that we're dealing with entire clusters means we're dealing with very large and very distant objects so it seems entirely possible that other intervening but non-visible normal matter may be conributing to the lensing in some but not all areas, which could both account for the apparent effect as measured (if an intervening source of gravity is acting on all the light) and/or distort the image (if the clusters and their surroundings are too large for all their light to be affected by the intervening gravity source(s)).

The root of my problem is the first two sentences of Dr. Carrolls article:

That would be a phenomenal accomplishment if proven true, but I'm concerned the potential phenomenon has made us to eager to accept inconclusive proof, in which case it is just "telling a story". Finding direct experimental evidence of dark matter would be awesome, but sounds rather challenging since it's only affected by gravity.