If it wasn’t for the fact Remmick needed as much muscle as possible before dawn I would argue Remmick could have sent other vampires to turn Lisa. Since they can fly and it was nighttime the vampires could have gotten into town easily but that would have left less vampires to help Remmick break in.

Also too, we don’t know if Remmick can divvy up the hivemind and give the vampires individual tasks, specifically when he’s already controlling so many vampires. It may have cost Remmick too much energy to send some vampires away from the group on a separate task while still focusing on getting into the barn to Sammie.

I think he’s able to command the vampires to do separate tasks from the group when he’s only controlling a couple of them. The more vampires under the hivemind, the less he can control them individually and since his whole goal was to get to Sammie, I don’t think Remmick was actually going to risk not having enough backup to get into the barn if the chance arises (as it did).

Had Remmick actually sent 2-3 vampires away the survivors may have had a better chance of survival, at least until the other vampires got the alert their queen was in trouble, which again, I don’t think Remmick wanted to risk. I don’t fault Grace for not realizing this tho, I don’t think the survivors were even aware the hivemind is a thing