This is what I think the stats should be
On Heal: Generates a wave of team-colored gas every 5 seconds near the medic and the healed target that slowly damages enemies (similar to the Heavy's Huo-Long Heater)

Gas: Gas field is slightly larger during overheal, does about 4-10 damage per second, lasts 6-12 seconds, dependant on how damaged the enemy was when he initially got hit by the gas.
6 Seconds/4 dps - Enemy is overhealed (does not matter how much overheal)
8 Seconds/6 dps - Enemy is at full health, not overhealed
10 Seconds/8 dps - Enemy health is at 65%-99%
12 Seconds/10 dps - Enemy health is 64% and lower

On Uber: All team-mates near the gas generate a slightly smaller wave of gas, heals all nearby team-mates for 5% of their max health (cannot overheal) every time the Medic generates a wave of gas

Gas does not trigger Dead Ringers (it's a rhyme :D)
+Uber lasts 6 seconds longer
+Pomson only removes 5% of ubercharge
- 10% Less Healing
- 10% Less Overheal
- 12% Slower Uber build-up
So what do you guys think?