Don't know about any other classes but Druid Aura's In the Coldburst-Nightchill Aura line are being dropped every time I zone.
happens on mana ripple line for enchanters as well, but not for twincast. Not sure this is a bug, but it is a bit annoying.
The short term aura was even shorter until recently. It's very possible you just assumed after zoning that the time had expired and reapplied. Maybe adjusting to the longer time now makes it more noticeable for you. In any event, the behavior of the short term auras haven't changed.