I think it's interesting that so many people have fallen in love with Dallas as 'dark horse' team in the West this year.
Dirk is still Dirk, so as long as he is still doing his thing Dallas is always going to be competitive. Then there's Ellis, who really seemed to finally find a team and offensive system he fits with. Parsons, meh, he's good but has become wildly overrated by far too many people. I think Houston actually improved by swapping Parsons for Ariza, due to Parsons lack of defense, particularly compared to Ariza who is near-elite on that end. Losing Marion probably hurts Dallas more than most realize.
As for the other additions, I don't see any of them as moving the needle much. Chandler is just about washed up, Felton is a over weight doughboy, who was probably the worst starting PG last year. Nelson was pretty mediocre the last few years too. Devin Harris is probably the best of that bunch of PG's. Losing Calderón is a big blow to Dallas as well.
I guess my outlook for Dallas is just far more bleak than most. I expect about similar results to last year, possibly they do worse.