Yes, I agree with your findings.
Once the liquid and media deteriorated, it's a goner, probably at best 10 - 20% heat extraction ability, I reckon.
I've seen these faulty heatpipes floated the ebay and market scenes to the lesser informed and innocence buyers, holes in pipes, visible re-solder works etc...
If you heat the heatsink, the heat would quickly dissipate to the fins is a good indication of good heatpipe.
I would be eager to see your experiment to rejuvenate the faulty heatpipe. IPA, 134a etc..
The RX24 Style Aluminum Housing Resistor say 25 to 30 watts form a good heat source for testing.
thanks.
Edit: Oh yeah, I think you need to vacuum the heatpipe for it to do its magic.