I am now at Dar as Salaam and I never guessed I would be having such troubles getting the bus ticket from Dar to Arusha and it is not like I could stop somebody on the road for arusha is all the way to the north of Tanzania and I need to reach Arusha within 2 days and though I have managed to find a reservation but for 18ooo Tanzanian shillings which I refused for the bus doesn't look even normal. Please, help!
I just got into Mombo two days ago from Dar and I had about the same problem finding a ticket from Dar anyway there is an SES bus provider and I bet they would manage to get you a normal bus ride from Dar to Arusha and if there is no any direct bus transport to Arusha you may first come to Mambo for I know from hear you may catch a bus to Arusha. Anyway if you are interested in this option up to the Mombo than you have a daily bus departing from Dar at 14h40 at the economic price of 14000 I guess.