Lots of triathletes here...Where are you from in Europe, Triman ?
About your Q : yes, deca helps with joints pain. I'm currently on a Eq/deca/anavar cycle. I had a periostite (I think it's the same word in english) at the beginning of the cycle and don't notice pain anymore now (week 6). In fact, I've added deca only to cure this pain and it really seems to work.
For the Dbol, I think you shouldn't notice really bloating with these doses, but take some proviron with it (50mg ed). It will keep all the water away, and it doesn't add stress to the liver (not a C17aa).
ALL the high androgenic AS are increasing RBC : Test, Adrol, Dbol, Masteron...Some studies shows that Dbol improves noticeably recovery times between high intensity workouts (for running). But AS are not equal for this. One more time, the best is Adrol, but with too much sides. You can try Dbol, but I think it's much better for a sprinter or a strength athlete than an endurance athlete (but at 15mg ed, you should't get too much size). If you compete for a 100m swimming/1km cycling/400m run, it could be a very good choice...just kidding. Take it for no more than 6 weeks, and tell us how it works. Will you stack it with something else ?