Yeah, If DDMence is giving you trouble giving Latias a Choice Scarf would be a good idea. You still have Raikou for Calm Minding.
I've been using this set and it works pretty well:
Latias@Choice Scarf
Nature: Timid
EVs: 82Hp, 176 Speed, 252 SpA
-Draco Meteor
-Thunderbolt
-Surf
-Trick
The 252 Special Attack EVs are obvious because you want to do as much damage as possible, 176 Speed EVs and a Timid Nature lets Latias hit a speed stat of 495, which is just enough to outrun a max speed Salamence after a Dragon Dance and the remaining EVs are just put into Hp to make Latias a little more bulky.
Latias can serve as your revenge killer in place of Heatran if you decide to give it a Choice Scarf but if you make this change things like Tyranitar and Mamoswine will have a much easier time against your team so I recommend replacing Heatran with a Swampert. A standard Mixpert would be fine, I think.
Swampert@Leftovers
Nature: Relaxed
Evs: 252Hp, 252 Def, 8 SpA
-Ice Beam
-Earthquake
-Surf
-Roar/Protect/Toxic
I recommend Toxic in the last slot, because it will help against bulky waters that could be annoying to your team if Raikou goes down early for some reason, and can also help wear down any Rotom that lacks rest who could be difficult to handle without Heatran.
Hope I helped. Good luck.