User blog comment:TheTobarMethod/Do AP's Need A QSS Upgrade?/@comment-7457593-20130905003924/@comment-1153246-20130907053850

For AP tenacity I run Mercs. If I need the tenacity more than the pen, Mercs is so worth it. (Alternatively, golem spirit is fairly cheap for what it gives, and you're not losing stats unless you're manaless, in which case you're only burning a little gold anyway.)