The best (in my opinion) thing to do with the deer is use it for raid (as sicXs suggested).
If you keep them separate at lvl 90 or so (depends on the hp of your tigs), you can do a cheap version of Ryatch's crazy raid team and bust out 80m.
Only works for android and full front:
Cyborg - niobe - tig - tig - niobe
Cyborg - leader - deer - prim deer
Many ways to improve on it of course (best version will be whatever Ryatch is running), but the above is the cheapest way to get the effect.