[quote=@Cu Chulainn]
<Snipped quote by 1Charak2>

Plus, the other five instances of Phantasmal Direhorse would have to manifest as well. It wouldn't be a monstrous beast you're pinned under, only a warhorse, if anything
[/quote]

That too, Considering that the horses are weaker then servants you could easily slay a horse, in order to get the time before it re manifests and delay the phantasm. At that point you can get up and crawl away. 

Still I can also see why Vance would be against it. As what happens if allied servants help pin down the condemned.