I've read the blog post - I think this removal is a huge regression.

It's often the case where adding a release like http://www.yodobashi.com/What-s-this-PSP-PlayStation-Portable-%E7%94%A8%E3%82%B2%E3%83%BC%E3%83%A0%E3%82%BD%E3%83%95%E3%83%88%E3%80%8E%E5%B9%95%E6%9C%ABRock%E3%80%8F%E2%98%85%E4%B8%BB%E9%A1%8C%E6%AD%8C/pd/100000009002050260/ requires the creation of a dozen artists. It used to be extremely fast to add such a release with the "Add Missing Entities" page (adding 12, or even 100 artists can be done by submitting a single page). Now, for each individual artist, you have to first perform a slow database search on the string, then wait for a slow creation request to submit and return the MBID - it's beyond slow.

The way I see it, the current lack of old functionality encourages the creation of bogus group artists since the UX is so awful.