Okay, being someone who has briefly studied Medieval medicine....and vaguely seen what they can do:
The Maesters do have a lot of drugs, an awful lot, and can deal with a wide range of afflictions. As you saw earlier, Jullon had his wound sealed with a cauterized sword (fucking hell, that was one of the most epic cauterizations ever) and that works, albeit being extremely painful and usually putting people into shock, though it is the only way to actually prevent infection. They can deal with poisons, if low-key and immediate, and they can also cure some diseases and wounds, applying a mixture of drugs, though transfusions and the like are not going to happen- there's prayer involved at times, because they just wouldn't know the anatomy well enough (also being why broken bones don't heal anywhere near as quick, though casts are used). Garland was lucky- if he were as old as Willas, he'd have certainly died from that wound, it's only relative youth that saved him there, because otherwise he'd be more susceptible. Other diseases we take for granted today that we can cure, the Maesters cannot, and infection, plagues, it's a horror story basically. When a plague hits, the costs and casualties of war are minuscule, I mean, shit like two-thirds of whole populaces dying out, wars breed disease and squalor so it multiplies it. Most soldiers die not fighting, but from the shits. Terrifying stuff.
@josephbCool- that's ideal. :)