Huh. You'd think that between their love of battle armor and having the Horses as neighbors, the Dominion would have loved the BA LB-X.
Maybe there will be something in Record Sheets 3150, whenever they finally come out.
According to the MUL:
Horses have access to the Black Wolf
Both sets of Falcons have the Ironhold
Clan Protectorate (by way of the Nova Cats) has both Thunderbirds
Basically all of the Dominion's current/former Clan neighbors have the BA LB-X. It may just come down to tactics and usage. Yes, the BA LB-X has its benefits, but I think the RD just prefers to use other weapons in similar roles. Most of the time an SRM rack can give that crit-seeking, maybe not as many clusters, but slightly better brackets. Anything that needs as many crit rolls as a point of BA LB-X can always just call in something that fills multiple other rolls like an Onirus C or a Fire Moth P.