Being a Skins fan, I can understand your confidence in the Fish. Having said that, the Skins D is going to be much improved. They were good stopping the run last year and should be even better this year with the additions of Pot Roast at the nose in the 3-4, Stephen Paea at one end and a healthy Jason Hatcher at the other. They have depth there as well and plan to rotate frequently to stay fresh. If I was a Lamar Miller fantasy owner, I would not be very confident heading into this game as I think the Skins will stuff him and force Tannehill to beat them via the air.
Now, having said THAT, the Skins have improved in personnel in the D-Backfield but that's like saying on a scale from 0 to 10 they have moved up from a 0 to a 2 or 3 in my opinion. Tannehill's WR's should be licking their chops. Any fantasy owners of Tannehill should be feeling good going into this game.
On other other side of the ball, Kirk Cousins is a considerable upgrade at QB over RG3 in this offensive (no pun intended...well, not yet at least) scheme. Look for the backup RB, Matt Jones, to spell Alfred Morris effectively. The Skins will run the ball and run it some more. That will be difficult to do though considering Suh is now on the Fish D-Line and they may stuff the run just like I expect the Skins D to do. In a game where who has to be most effective potentially via the air, the nod goes to Tannehill in the QB matchup while the nod goes to Washington on the WR's as I think Jackson and Garcon are better weapons than what Tannehill has at his disposal.
The difference may be special teams and this is where Miami likely has a huge advantage. Again, any improvement by Washington would be moving up from a grade of 0 last year. Watch for former Duke WR and current Skins rookie Jamison Crowder in the punt return game. He could make a difference.
I know the Skins have been a soap opera and circus over preseason (and pretty much ongoing for years under Danny Boy) this year, but one thing that has gone unmentioned is that they looked pretty darn good in preseason and have made a lot of solid personnel moves - particularly on the defensive side of the ball, in the draft, and moving Cousins to the starter giving the team at least a chance. Covering 3 1/2 on the road is difficult so buyer beware. I'm leaving it alone. Same reason I shied away from laying 2 1/2 on the Colts in Buffalo. On the one hand, it looks too easy with Tyrod Taylor vs Andrew Luck in the QB battle. But, the Bills are at home, have a great defense, and the Colts defense is porous. Glad to finally discuss real NFL football. Good luck this weekend, mate.