I've been playing around with my Heavy Attack sorc and I've used the scalding flame rune in order to trigger empower to buff my light/heavy attacks through the mage guild passive (Casting ability grants empower for 3 seconds), and while it works, it just made me realize how badly the mage's guild skill tree needs a spamable to work with this passive. All of the mage guild damage abilities are ultimates (Meteor) or damage over time abilities (Entropy, scalding rune). Perhaps the major sorcery from Entropy can be moved to the Rune, and then Entropy can be replaced with a spamable ability that can be used to proc empower so that no damage is wasted from the rune's DoT proc? Alternatively, I wouldn't object to things being kept the way they are, but having empower duration extended to match the burning duration of the rune.
Just a couple of thoughts.