I'm pretty sure that the Heralds had Honorblades, and that the Dawnshards were something different, could just be different names for the same thing, and it's not a real problem but yeah. Anyway, I really like this, although it does beg the question of why they don't use them against the Alethi.
That sounds about right to me.
A couple problems with this one, firstly being that a Shards cognitive aspect only affects the population of their Shardworld in small ways, it's not a big effect so it shouldn't cause people to act less honorably really. Secondly the KR have already gained their powers, I don't think that they had variable strength due to how honorable they are, and as they were heavily invested with Honor anyway, the splintering shouldn't really affect their Honorability at all. Third that's the second oath of the Windrunners, not the first of all the KR. The first oath is
"Life before death, strength before weakness, journey before destination."