Copying the link and sending it to the whole realm is how things used to be done. To make things less tedious, and I think to incentivize the use of armies, army members now have a clickable link on their scout reports that states "share scout report with your army" (or something along those lines), which opens a little 2 second confirmation window and sends the link to the army members.
The old method is more laborious, one has to select the link, copy it, click on messages, click on send to realm (not to mention scrolling to find the right link), click on the text box, paste, and then click to send. Often it involves shifting through multiple tabs, back and forth, to get all the links in one message.
I don't really feel like limiting the scout reports to only one's army, when clicking the link, really yields any benefit these days. I'd really link for my scout reports to be available to the other marshal, and for his to be available to me. Getting scout reports in a timely fashion is nowhere near as common as it used to be.
