Thanks to PolyGeo for the missing piece..

First setup Iterate Feature Classes to loop through all your feature classes in a workspace, this will feed them one at a time into your next process, but if you put Collect Values as the next step in your process it will 'clump' all the individual feature classes into a cohesive input for Merge..

This workflow produced a merged feature class from all the feature classes in the workspace Area11_14.

First setup Iterate Feature Classes to loop through all your feature classes in a workspace, this will feed them one at a time into your next process, but if you put Collect Values as the next step in your process it will 'clump' all the individual feature classes into a cohesive input for Merge..

This workflow produced a merged feature class from all the feature classes in the workspace Area11_14.