Reading the compendium article, it's a bit unclear.
closed as unclear what you're asking by Brian Ballsun-Stanton♦ Feb 16 at 11:36
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Yes, that's the At-will you bring in from that side of your hybrid. Typically Hybrids get an at-will from each of their classes, the Blackguard doesn't get Vengeance Strike, instead he gets the at-will from his Vice.
If you pull this in the character builder it's far clearer. When you select your Vice it says "Level 1 At-Will Dominator's Strike"
One of the Blackguard class features is Vice At-Will Power. This contains Dominator's Strike and Ferocious Strike. Hybrid Blackguards lack this feature, in my opinion this means that they can choose any Paladin at-will power. In the online character builder, at Powers you can freely select your Paladin at-will power, Dominator's Strike is not even a default.
Normally non-hybrid classes get 2 at-will powers chosen freely. Some classes restrict that, Blackguards and Warlocks for example do. You know this because the class descrpition says so.
If you do not find something similar by Hybrid Blackguards is because there is no restriction.
This has the strange consequence that Hybrid Blackguards have a better power selection than non-hybrids. Now you can dump Strength, and use Charisma as a primary, or use the various Domain feats.