For a lot of the services I'm thinking of for this case the scheduling may be across multiple nodes but it may not be flexible - e.g. this is my preferred way to run things which need guaranteed local iops. So Swarm maybe helps with service discovery etc. but its main purpose is lost.

I have a lot of complaints about Docker Swarm but they're either about its ownership issues or relatively minor (but - lots of minor) issues, if you want to use it it's fine. But you do still need an orchestration layer above it anyway.