Blizzard has noted that Trail of Cinders was a "bug", and that originally it was only meant to do 300% weapon dps instead of 1500%. So all of you Demon Hunters out there, enjoy it while it lasts. It will be changing next patch (1.0.5). The full post can be found below.
Blizzard tracker: August 31, 2012
In patch 1.0.5, we will be fixing a bug with Trail of Cinders that is causing the rune to deal five times more damage than intended. As a result of this fix, the amount of damage done by Trail of Cinders will be reduced from its current value (1500% weapon damage over 3 seconds) to the value we originally designed for 1.0.4, which is 300% weapon damage over 3 seconds. While this bug was discovered very quickly after 1.0.4 released and is capable of being hotfixed, we didn't want to move forward with the fix without giving players proper notice. We also know that players are having fun using Trail of Cinders in their builds, so -- although this is an important issue we want to address -- we're opting to wait for the next client patch to make any adjustments.
We recognize that some builds which currently use Trail of Cinders will no longer be viable once this bug is fixed. Ultimately, we want to continue to provide players with more build options and ways to feel creative with their skill/gear selections, but not at the expense of going against our design goals or creating situations which can encourage players to limit themselves defensively.
Discipline-based skills were never intended to trump Hatred-based skills when it comes to dealing damage. Instead, Discipline should be something you build up and save to use defensively, or to provide utility in addition to dealing damage. Allowing Trail of Cinders to remain in its current form goes against this philosophy, and in addition creates risky scenarios for players (after all, if you’re incentivized to spend all your Discipline doing damage, it won’t be available when you need it to keep yourself alive with skills like Smoke Screen or Shadow Power).
We don't yet have a date for when 1.0.5 will be released, but we'll provide more information as the development process continues. We'll also update this thread with a reminder once we're close to releasing the patch.