Well after level 16, with probably about 15-20 being Veteran horse archers (speaking from Namian side), you can take down 80 Merkits with a party of just 35. Although it's always better to even the battles so your party death toll doesnt pile too high. Depends on how quick you are, id recommend not using armoured horses but the fastest ones (43+ speed). I can handle 60 soldiers in my party, i can take down well over 100 merkits with only losing at the most 5 soldiers. It gets better as your level progresses, which i can safely say plays out better than Native when lvl 20 makes you god.... I havent tested it out on Chin armies yet, but i imagine the results would look simular.... but with a more chance of losing half your troops since the Chin army is heavily armoured.