Yes, Dead Orbit has so far been useful. They're using their fleet to provide valuable intelligence to the Vanguard. Here's the problem though, their endgame is we abandon Earth and aggressively expand across the stars until no single threat can hurt us. While not a bad plan on paper, we know for a fact that this plan is a dead end for us. Even if we had the men and materiel for this undertaking (we probably don't), the plan is impossible long term. The very philosophy of the Darkness demands our extinction, and it has consumed civilizations many times more expansive than Dead Orbit can even begin to dream of. It can't be outrun. The only entity with even the slightest chance of beating it back is the Traveler. Where's the Traveler? Why, it's sitting in a coma over Earth, the planet Dead Orbit wants to abandon.