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I thank you both for your informative comments. Chrome on my N5 while experience wise runs fine still heats the phone excessively.

A quick Google based on your nand theory suggests I run fstrim:

"Due to a bug with the driver for the Nexus 7’s internal Samsung NAND storage, Android on the Nexus 7 was not properly issuing TRIM commands to clear unused sectors. This caused write speeds to slow down dramatically. This was fixed in Android 4.1.2, and Android should now properly be issuing TRIM commands to the internal storage."..."However, this update does nothing to fix existing sectors that should have been TRIMMed in the past, but were not"

I'll give this a bash, then downgrade, then consider a replacement tablet.