I believe in 2005 they did for the 2.5L non-turbo engine. I would personally skip the 2004 Outback as it is the older design and not in the same class of car as the newer 05-09 redesign.
I own a 2004 WRX with 2.0L and active in related forums and have never heard of a blown head gasket for turbo 2.0L or turbo 2.5L except where the owner kept driving without any coolant in the engine.
Consumer Reports last I looked shows major engine trouble (head gaskets presumably) up to 2003/2004. 2005 the non turbo engine is well above average.