Scouts & Explorers make great medics. You can usually get at least one, maybe two level 1 medic promotions for your early Scouts from animals.
By mid-classical era, you might be able to produce level 2 medic promoted Explorers (barracks, civics, GGs, and the charismatic trait would definitely help).
These specialized medics allow you to promote the important combat promotions for your fighting units.
Anyhow, I think Fixaris did a great job with unit-balancing in Civ IV. All the units have their uses -- at least, I've used every single one of them. The only unit I can think of that has a really short lifespan is the Musketmen, but even they have their uses.
Whereas, Ironclads have their uses when the AIs frigates & galleons just dropped off their boarding party on your soil (which will all be crushed the following turn), and then decided to stick around your coastlines serving as naval blockades. You can really use a couple of Ironclads then.