I stumbled across your post after experiencing the same hg failure you describe. We own a 2001 Subaru Outback with the 2.5L engine and at 99,988 miles our hg failed. Keep in mind this is a 9 year old car that has been driven a little over 10,000 miles a year since it was bought. The conditioner was added to our car, but alas, the conditioner is not a problem solver/fixer. The hg was poorly designed. Instead of SOA owning their mistake in design (which I’m sure they decided to option to do the right thing for customers would cost too much since you have to remove the engine to replace head gaskets), they slap a band aid on the issue.
I will never buy nor recommend a Subaru to anyone. It is inexcusable to make a $30,000 car that require major engine repair before 150,000 miles. To not value the customer experience is even more revealing of Subaru’s company culture. I’m going back to Honda as soon as I get my 5 ton station wagon out of the shop. I refuse to drive a time bomb any longer.