I'm not sure this is worth the investment, any thoughts?
No, they arent worth as an investment and as you calculated its clearly seen or displayed that you wont really end up on profits but rather you would really be on loss.

 feedback on the mentioned companies? other recommendations?

Hashflare is legit i dont know about nuvoo.io since its just new into my ears but i dont really recommend anyone of them since its not really worth as an investment.