"A virus with high mortaility and rapid spread will rapidly kill all susceptible individuals within it's catchment area, so it's likely that such things have never really gotten off the evolutionary drawing board."
Generally speaking I agree, but only when the virus is lethal to all susceptible individuals.
If the virus is non-lethal to some susceptible individuals then those individuals could become carriers (a reservoir where the virus can continue reproduce but does not kill its host). Carriers are how a virus can have a high mortaility and rapid spread without becoming an evolutionary dead-end.
In the case of Ebola I have heard that it is suspected that fruit bats are carriers. If it is true that fruit bats are Ebola carriers then I think that means Ebola has some susceptible individuals (humans) where it is highly lethal and some susceptible individuals (fruit bats) where it is non-lethal.