I looked around the door seal and it looks fine.
Where else should I look?
The door mirror?

(on one owner 2004 RX8 with 41k miles)

 

I have the same problem. Got it fixed before and they said it was the hose leaking from the sunroof. Now it gets wet when I take a turn for the first time after I've been sitting still. I think it might be from the wiper area.

 

Are you from leaf-country? If so, you may have a plugged drain. There's a major drain kinda under the brake master cylinder over in a corner next to the firewall and 1/2 way down. Is the lower driver's door panel wet? Could be drains plugged in the door. There are also drains for the fresh air intake plenum, but I don't offhand know where they are located. It's unlikely to be a sunroof drain without getting stains on the headliner or A pillar somewhere.

 

Ok- actually saw a big drop under the driver's side door mirror insdide panel (ready to drop off onto door panel). So it must be the mirror. Is there a rubber gasket in there? Maybe gunk gets in there and causes an issue (like the tail lights)

Oh- and no sunroof. Me no fit with sunroof. I was lucky to find a base 6 speed manual with just the manual sports package.

 

Have you routed any cables through the firewall? If so, check your seal.