This is probably SBT's greatest weakness and Gradle's biggest strength, relatively. I've never run in to this personally, probably because I'm use Nexus[1] as a repository cache. My understanding is that the underlying problem is a limitation of the dependency resolution library they use, Ivy[2]. Gradle used to use this but at some point wrote their own dependency resolution library. There are some improvements in recent versions of SBT but you have do a little configuration. See here[3] for more details.
I also thought of introducing Nexus, but since we are only 3 Devlopers (yet, we searching though) it didn't too much sense. I also I hoped for Nexus 3 (but since I'm waiting over half a year now, we might introduce Nexus 2).
Oh and we also using the Cache, when working on newer sbt projects.
Oh and we also using the Cache, when working on newer sbt projects.