es2015 preset doesn't transform async functions. Consider using babel-preset-env. Also, you can use es2017 preset alongside es2015 to convert everything to ES5, but it's generally better to use babel-preset-env.
Using babili and uglify. I assume you're bundling/calling webpack as webpack -p as this includes Uglify Plugin as the last step. Also, you're using Babili in your babelrc. Uglify doesn't understand ES6 (uglify-es does). Use only one minifier - it's not necessary to use both babili and Uglify.
Using babili as another preset in babelrc. There are some issues with babili when used along with es2015 preset, consider using babili-webpack-plugin and do NOT run webpack with webpack -p as it includes UglifyJS. More about why to use babili-webpack-plugin is in its own docs.
https://www.npmjs.com/package/babili-webpack-plugin