This is the setup i use
Offensive Black orc Warboss
Black orc BSB with the spirit totem
Gobbo on wolf with one hit wonda and brimstone bauble
lv 1 night gobbo scroll caddy
This gives me 6 DD and 2 scrolls - just the right amount for me
If you want more magic defence, swap the gobbo on wolf for another lv1 shaman with staff of sneaky stealin. This gives you 8 DD, - 1 to enemy, 2 scrolls. A little overboard if you ask me (especially if you come up against dwarves or other armies with little/no magic offence Eg. Bretts, wood elves, empire etc etc)
I prefer my setup as it only takes one hero slot (not including the BSB), but it depends on who your apponents are.
I cant really help you with magic offence as i never use it with O&G, however i imagine you would need a lv4 Orc shaman.
Hope this helps