Good point.
Or make it possible to queue a second (no more!) healing, perhaps only if applied by a medic.
Maybe let the syringe do damage over time to specimen (not much; perhaps for medics only).
So even if you know you're dying because you have the syringe ready and not a weapon, while surprisingly facing a scrake or FP, you know that you "helped" the team a little bit in your last seconds...
In my opinion, the medic perk is very useful, if the teamplay is right.
As often encounterd in "random teams", players often split up, making it even more difficult to heal effectivly.
If the team sets up a "frontline", the medic has the oppertunity to unfold his full potenial form the "second line".
It's although essential that the other players have fate in the medic. Runing away scared while down to under 50% heath, making it difficult for the medic and leaving a big hole in the defence, may screw the whole team.