We recently encountered this issue.  The SmO create reference to get the destination is outside of the Task step.

The SmO step is placed on top of the Multi-Step.

K2 Five 5.2 FP27 behavior is that it ran the destination task rule first, then executes the mult-step in the order.

We had to extract the logic to get the destination value in a separate activity in the process.

Now each task has an extra step showing in the process flow. (not user friendly when viewing business process)

Why can't the activity destination rule be evalated at the Task level after all preceding steps are executed? 

"At runtime the destination is set at activity level"

https://help.k2.com/onlinehelp/k2five/userguide/5.0/default.htm#K2_Workflow_Designer/Use/Canvas/MultiSteps/Create-Multi-Steps.htm

• When you add a Create Reference and Task step in the same multi-step and then use the email reference (created from a SmartObject in the Create Reference step) as the destination email (assigned recipient) in the Task step, the following runtime error occurs “An Activity with a client event should at least have one destination”. At runtime the destination is set at activity level and having the Create Reference step in the same multi-step as the task prevents the destination reference from executing it as it should. Rather drag the Create Reference step out of the multi-step so this can execute before the Task step