It's a start. There will be ways around the mute filters by using alternative spellings, substituting in similar unicode characters, etc.

There needs to be a "quality" score for a Twitter user and an option to mute tweets from "low quality" users. Quality could be determined by utilizing an algorithm similar to Google Page Rank. Retweets, likes, and follows by "quality" users would be considered in a user's quality rank. Reports of hateful conduct would be weighted in as well.

It's too bad that it has taken this long for Twitter to even -start- to address the abuse. They are lucky they have no direct competitors.