This card will only ever mildly inconvenience the Corp, even when used against a scoring server, even when the runner has managed to Account Siphon or #Vamp the corp. A Noise: Hacker Extraordinaire deck that just wants to mill out the corp can consider playing this card for its cheap install cost, but since it takes up 1 it will probably get sold to Aesop's Pawnshop before long anyway.
Now considering targets, either the scoring server already had plenty of Ice or the corp can just start building up a new scoring server. This means the corp will only need to pay to install upgrades or agendas in that server. Now if you manage to put 3 Diwans on a single server then the corp will probably purge. This means you've spent 3 and 3 and tied up 3 to force the corp to spend 3 (and mill 3 cards if you're Noise). You will also have had all your other virus counters purged as well. Likely you will have spent additional and to tutor or recur the Diwans in the first place since it's quite unlikely to just draw all 3 of them in the first place.