Whatever happened, both aeroplanes *should* have been aware of each other at a towered field and should have been keeping a very good look out. If I couldn't see the other traffic I'd deliberately throw in a few more phrases onto the RT like "joining crosswind for 20, over the numbers at 1000" or something to help them as well as me. Likewise when I am coming into an untowered field, I'll report something like "5 miles south at 1500, positioning for base leg join 25". The more pertinent info the better if you ask me.
The DA40 doesn't have any blind spots like the windcreen pillar in the coventry accident and has good vis. I imagine the RV has good vis too.