Good signing, I'll give it a B grade as it's certainly not a bargain, but Kamara doesn't have an extensive injury history (see my F grade for Cook) and doesn't have too many carries on his body, and is one of the best receiving backs in the NFL (even better than Cook). The Saints are also going to be approaching a cheap QB option well within this span and Kamara will be a MASSIVE help to any new QB once Brees retires and the money here will be a non-factor in a few years.
Can't give it an A grade as it's not a bargain signing, but still overall positive.