Right you can import language pack, but there no detailed information shown about actual phrases/e-mail templates that were added/changed/deleted in the process. Maybe this information isn't that important to average website administrator, however it's invaluable for Deployment Script.
Sometimes, while working with Deployment Script, I see situations where phrases are reported as being deleted locally, but I'm sure I wasn't deleting anything. It all ends with fact, that some part of /modules/custom/install/english.lang file wasn't imported. Without import log this is pretty hard to analyze later on.