This might not actually be a bug, but I’ll bring it up in case it is.
Certain skills do not queue properly; for example, using Symbol of Wrath, Flashing Blade, Leap of Faith, and any spirit weapon summon on the guardian, then trying to queue another skill will cause the second skill to start animating like it’s queued, but then the first skill completes and the second skill just doesn’t happen.
At first I thought it was a result of some kind of queue timeout, but it seems to happen regardless of how long or short the wait between the two skills is. At the same time I’ve been able to queue other skills with fairly lengthy cast times. I believe ZD > another skill queues properly.