Is the Block Bad Queries Plugin Still Relevant?

Yes it is still relevant, WordPress is very subject to query based attacks. It is more common and easier to attack bad plugins/themes, so even if your WordPress version is kept up to date, it’s still a good idea.

There is a better plugin called Mute Screamer, it uses a central PHPIDS database.

http://wordpress.org/extend/plugins/mute-screamer/