I think it is possible that making any kind of gesture to Jake, even if it is a condolence card to his agency - is a bit presumptuous, and that is why it feels a litle "weird" to me too. Would we send one to Maggie? to Christian Bale, who was his co-star on "Dark Knight"? how about Christopher Plummer, his co-star on "Imaginarium" or Abbie Cornish, his co-star on "Candy" or Sienna Miller, his co-star in "Casanova", all more recent than Brokeback? Put into that context- that they were co-stars AND FRIENDS, which Plummer and Bale certainly counted Heath as a friend, it seems mildly silly to send a condolence to them since we are not friends of theirs nor know them.
I think the implication is somehow that assuming a special friendship, or a "special friendship" because of the exaggerated idea we may have of how important Heath was to Jake, is somewhat inappropriate. They weren't living together as lovers, nor can we assume that he was any closer to Heath than his many other co-stars. I think that is the weird thing, and I don't think any gesture of condolence to Jake would really be of any greater utility than the one we made that is photographed in our banner.