Spine -> Unity -> Instantiate (Mecanim) is our current workflow.
In 5.1 they will introduce variables for mecanim that allow you to directly map the a state animation speed, so I plan on making AttackSpeed and MovementSpeed and mapping these to each state which can be affected by each. If a player gets chilled I will slow AttackSpeed and all the speed properties of mecanim will be adjusted which is a feature I've been waiting on forever.
The concern is Spine uses time based animations. How can this translate or what would we do to get Spine to play nicely with this mecanim feature and also ensure events are still fired correctly from mecanim. We are not using mecanim events because speed > 1 can sometimes cause events to not fire, it's very unreliable... Spine events always fire.