There are plenty of wounded, dead and dying figures, you just have to know where to look for them. As mentioned the Airfix WWI German dead guy will work for any army with the pith helmet or even with the spike helmet, the US Army wore them for about 30 years. The Pegasus Berlin Germans has a rather generic dead guy in it, a quick head swap and he can be almost anyone with a greatcoat. Pegasus two Russian Infantry sets and their Waffen SS set 2 have Russian and German dead infantry, both for WWII.
Ykreol makes whole sets of dead guys. Their latest set is Custer's Last Stand, its a whole set of over fifty dead soldiers and horses. Many of their sets are ancient or Napoleonic sets, with several whole sets of WWII dead guys.
Many metal figure sets make dead and wounded guys. Dead and wounded guys can be converted from other poses. I personally have essentially no use for dead and wounded. The only way I would support dead and wounded figures would be in context with a medical aid station set.
Atlantic used to do a pretty good medical set, with doctors, nurses, stretchers, and stretcher bearers and chaplain. That type of set would be very useful for both wargamers and diorama builders. Medical sets for French Napoleonic would be a good set for HaT, since they already make the ambulances.