Is there a macro or function within Cubase 8 that allows me to apply overlapping of midi notes to selected midi events by just a few ticks, enough to activate legato?
Yes indeed 
…
There is MIDI menu>Functions>Legato, and two related settings in Preferences>Editing>MIDI…
- Legato Overlap (can even be set to a negative value ), and the option, “Legato Mode: Between Selected Notes Only”.
Fantastic! Will save me a lot of time. Thanks!