For the left circular object, I created an aramture, rotated it and applied it to a circle.
For the second, I did the same, but applied the rotation to the armature.
Note:
the left circle is upside down in Krom. I guess this is due to not appling the rotation of the armature.
the right circle is at a different position in Krom. No idea why this is so.
Is this behavior expected or should I file a bug report?
I only played around with your blend file briefly, but I got the top right one working by setting the circle object to have the same world origin/center as your armature (and as Monte says, it’s a good idea to apply scale and rotation too). - They seem to need to have the same centerpoints to function correctly in Armory.
As for the left circle, I can’t seem to get it working for some reason, I don’t know if it might be the 4th bone not applied a vertex group that Armory might somehow take into consideration relationship wise, but I’ve no clue