Just a thought, have you tried www.dabbleboard.com? It might be what you're looking for to do your diagraming.
Otherwise, Viso has a steeper learning curve, but probably has more tools for what you're doing. I know it's expensive to buy, but with a Bizspark membership (get sponsored and only pay $100 after 3 years) it's free for the downloading along with your MSDN membership.
Otherwise, Viso has a steeper learning curve, but probably has more tools for what you're doing. I know it's expensive to buy, but with a Bizspark membership (get sponsored and only pay $100 after 3 years) it's free for the downloading along with your MSDN membership.