Instant fountain heal disincentivizes healing allies
The instant heal is not that big of a deal to the killer getting downs. But it does prevent allies from healing eachother and getting their altruism points.
I propose making the fountains heal half a health state rather than a full one so survivors have an opportunity to heal. It is very rare that you get injured against The Plague without also getting sick. This means it is a much worse option to get a heal from a survivor, since fountains are so quick and easy to use. With my idea, they take 5 seconds to heal half a health state instead of the standard 8, then it would take 8 seconds for an ally to finish healing you. This cuts down healing time by around 3 seconds, or 11 seconds if you are using self care with no speed boost.
An alternate solution would be to make fountains take 15 seconds (preserved progress) to cure your sickness. This would simultaneously resolve the issue of sickness being too easy to remove (therefore preventing survivors from spreading it.) However, the downside to this would be that it would be yet another "hold action button for a long time" interaction which the community is starting to hate thanks to legion.