Yes, with doctors & others. If you have to share results with doctor in plain text what is the point of having it encrypted in the first place? The data will just leak out.
If its private; its not really decentralised. If distributed is what you were looking for there are much efficient solutions available.
With data which you want at realtime basis; do you want a headless organisation who have no QoS guarantee or a organisation whom you can sue for poor QoS?
Incorrect; #blockchain is by design slow. Bitcoin makes a block every 10 minutes. 10 minutes delay in medicine is life/death.
You may but that would result in more blocks which leads to more storage. With #blockchain already we are wasting space by replicating data across all full nodes, how much data storage do we want to waste?
Not really, #blockchain isn't a database. It's more like a table or rather an append-only log. You can't do a relationship mapping between a patient, doctor and illness.
I hope someday someone will be able to change that.