The log snippet below is only one log, but it is representative of what it takes to kill imperial warhorses and armored warhorses. At the time, we were raiding Losache Keep (the battle where Alaric's amulet was shattered) and my character had Herculean strength, high level frenzy and was using a highly enchanted two-handed straight dagger.
I cut out the rounds in between the circles. A similarly buffed circle to Alaric did 33% through sanctuary.
Draw your own conclusions:
Code:
A skinny male human fades into existence.
A skinny male human's circle stab decimates an armored imperial warhorse.
[HP: 89%] [ME: 32%] [PE: 94%]
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A skinny male human's circle stab MUTILATES an armored imperial warhorse!
Trinton utters the words, 'gszabra ay yauhp'.
A bright spear of light appears in Trinton's hand!
Trinton's faithful spear sails wide, but a bestial male human still cringes in pain.
[HP: 86%] [ME: 32%] [PE: 94%]
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A skinny male human's circle stab DISMEMBERS an armored imperial warhorse!
A skinny male human's circle stab does UNSPEAKABLE THINGS to an armored imperial warhorse!
An armored imperial warhorse is DEAD!!
You hear an armored imperial warhorse's death cry.
A skinny male human junks a corpse of an armored imperial warhorse.