If there are multiple entry points (i.e lots of bundles) then Elm is not very good at parallelizing shared asset control.
Elm-make is slow, and if the dependency tree triggers an expensive change, then it's important to realise that Elm causes a slow re-compile - but webpack is responsible for filling up memory, and therefore slowing everything down
Webpack can segfault (and does if you aren't careful)
github.com/elm-community/elm-webpa... switches the way that node-elm-compiler was looking for dependencies, and helped fix a pretty bad problem of opening too many things.
To expand on the Webpack issues:
I worked on this a bit to help fix it: