This is a pretty cool team, and I am glad to see more people utilizing DDMence in this meta. It is an extremely underrated sweeper who has potential to do a lot of damage. However, one of DDMence's best quality's in this meta is its good speed stat and its ability to outspeed Scarf Genesect. Your current set doesn't take advantage of this, so I would heavily recommend 8 HP / 248 Atk / 252 Spd
with a Jolly Nature.
You seem to like 8 HP, so I took 4 out of attack rather than speed. This helps a lot vs opposing Scarf Jirachi's and Salamence's, as you can now speed tie them and are harder to revenge.
Also to help with your weakness to sun teams, I would recommend Specially Defensive Zapdos
over Rotom-W. Zapdos gives you a considerable amount of Special Bulk, much like Rotom-W, but it isn't as weak to Venusaur. It is still a fantastic check to Rain sweepers, like Tornadus-T, and can be very difficult for some rain teams to take down. Hope I helped.
Zapdos @ Leftovers
EVs: 248 HP / 76 Def / 184 SDef
Calm Nature (+SDef, -Atk)
- Heat Wave
- Hidden Power [Ice]