Medic is probably one of the best balanced of the four perks right now. If anything, some of his skills need nerfing.
Tier 1: Medic doesn't have ammo problems unless forced to clinch a wave, but if the medic is having to carry, you're doing it wrong. Enforcer needs to be looked at in comparison to Healing Surge. As it stands, the latter is undeniably better.
Tier 2: These two perks are fine, save for a few issues. Armament should not work when armor reaches zero. How can you repair something you no longer have? Also, there is a slight bug between the two skills, one I've reported that hopefully gets fixed.
Tier 3: For this, Regeneration is the skill to take, mainly because Laceration does nothing. I initially thought Laceration would be helpful, since headless zeds stumbling around are an issue with the medic's garbage power guns. I figured the bleed damage would cause them to drop faster without having to punch them or waste rounds in their carcasses. It doesn't. Regeneration allows you to shrug off siren damage and minor scratches. On higher diffs this is critical, as self-healing takes a long time, and you don't have time for that on sui+.
Tier 4: Most take Vaccination because they want to be "good little medics" and get a boost to the already broken Armament skill. The bloat bile resistance is irrelevant; as it stands, this is just Armament+. For myself, I take Acidic Compound. The panic effect of this nifty skill causes Husks, Sirens, Fleshpounds, and Scrakes to stop whatever they're doing for a good three seconds, even attacking, and all it takes is a dart shot. Add this to the medic nade, and you have some serious crowd control potential. In short, Vaccination is just another Armament and needs looking at.
Tier 5: Neither of these are particularly useful, but they are fine as they are. Airborne Agent for better healing, Sedative for some serious disabling power, whatever your preference.
And I'm going to be frank on this: medic should have lower movespeed. Not by much, but it needs to come down a tad. I never comprehended the medic having such outrageously high movespeed in KF1 either. He needs to be a bit quicker on his feet, not a full on sprinter like zerk.