restore datasheet functionality
SharePoint 2013 degraded the datasheet view, purportedly to make it platform-independent; but this rendered it impossible to paste multiple rows of new data into a list as before.
I regularly paste 100's of rows at a time from excel into datasheet view. But you do have to ensure you match your columns!
Tom Burke commented
It's actually not impossible, but it has to be done in IE and everything has to be exactly-perfectly-right, with the same columns from source to destination, and Jupiter in the 11th cusp of the Milky Way. It takes some finagling and IE usually prompts each time to allow the copy/paste (which I believe is a configurable browser setting). Try just highlighting the top-left cell, as well, and pasting from there.