What happened to my-*.cnf in MySQL 5.6.8?
You know what they say, about "when all else fails..."


  This release continues the process begun in MySQL 5.6.6 of making
  changes to the default values of server parameters. The motivation for
  these changes is to provide better out-of-box performance and to
  reduce the need for database administrators to change settings
  manually. These changes are subject to revision in future releases as
  we gain feedback.


This is all explained in the Release Notes for MySQL 5.6.8.


  On Unix platforms, mysql_install_db now creates a default option file
  named my.cnf in the base installation directory. This file is created
  from a template included in the distribution package named
  my-default.cnf. You can find the template in or under the base
  installation directory. When started using mysqld_safe, the server
  uses my.cnf file by default. If my.cnf already exists,
  mysql_install_db assumes it to be in use and writes a new file named
  my-new.cnf instead.
  
  The my-default.cnf template replaces the older sample option files
  (my-small.cnf, my-medium.cnf, and so forth), which are no longer
  distributed.


Without question, innodb_buffer_pool_size is the single most important tuning parameter for a MySQL installation.

For "sensible defaults," start with the defaults.  

To put it another way...


  "Tuning" your server can be a stunning waste of time.


-- Schwartz, Baron; Zaitsev, Peter; Tkachenko, Vadim (2012-03-05). High Performance MySQL: Optimization, Backups, and Replication (Kindle Location 12182). OReilly Media - A. Kindle Edition.