I have quite a few battles where I got around 30 wounded and 0 dead.
If you look at the % "casualty survival chance" given in your medicine stat for saving a troop, what does it say? I hired a surgeon who has 87 in medicine and the bonus provided says +0.9 %. Forgive me, but I think there are other confounding factors contributing to your "30 wounded."
1. Does the enemy have mostly blunt weapons? Maces and the like have 0 chance to kill, only wound. The Aserai in particular are fond of arming their troops with maces.
2. Companions can only be wounded (unless you turn on character death).
3. There is a base chance, too. In Warband it was 25%. According to the game itself, the medicine skill is only helping around 1% of the time. Meaning, if 100 of your troops were to otherwise fail their chance at being wounded, your surgeon will only save one of them.
Being early access, it's
possible that medicine is giving more chance than it says it does, but I doubt it would be that significant.