Had a quick game with Bogarus and there troops suck big time!
Indi heavy infantry managed to defeat my massed hordes Voi archers protected by Peshti spearmen 4 turns in a row. Just expanding through indies is hard with Bogarus troops.
I agree with Dr.P, a awake SC is a virtual must. If I was in a MP and Bogarus was my neighbour, guess who I would attack first? Bogarus may become even more a favourite target for an early kill then Ulm.
Not sure about the sloth 3, I think you need resources to recruit your one and only decent troop type Malaia Druzhina. Those guys are decent, them plus a awake SC should keep you safe in the early game until you get your excellent magic and research going.
Mid/late game Bogarus will become a nation of summoned troops backed by powerful magic, with lots of options.