Purty much. The twins are pretty dead, sadly- the only way I can realistically see them coming back is via the Embrace, by the time anyone actually gets to them it will be far too late. Because the blood loss would be too great, and I see them dying pretty quickly.
And as Mike mentioned, realistically, even if you did somehow miraculously bring back Isa/Nessa's heart (which would make me call BS- Tom too can pull off pretty miraculous healing in true form, as could someone with the right amount of experience with Ruby like Rin, but I highly doubt either could save Isa and Nessa at this point), the brain damage would be too great from the lack of oxygen to her brain. Both twins would likely lose brain functioning, and that's a pretty awful state to bring them back in.
Plus as Daiki himself pretty much showed by doing this in the first place and his own words, he's cool with his characters being dead. He wouldn'tve killed them himself if that wasn't the case. I found it pretty shocking too, but that's Daiki's choice to make in the matter, and that choice should be respected. It does create quite a bit of tension, what with the Ruu and Jack fight, as I genuinely don't know how the fight will turn out (though it seems it's likely to be Jack's win. Poor Ruu, even if he did just kill three people, two innocent).
But don't force healing onto other characters where it's both contrived and unrealistic. It removes any sense of consequence and weight to what just happened, at least to the twins, and I honestly don't think it serves the story well to cheapen the deaths for those whose deaths are not already cheap (and by that, I mean those who can just shrug off death and come back).
...Also, still waiting on Mooncake before I go. ^^" I need an idea of Lucas's current position and how he was affected by both Shirou and the wards before I can move with my characters, particularly Tom.