I think the Blend method is not a good one. It will result in uneven spacing of the arrowheads when a curved path with variously lengthed handles is used as a new spine.
None of the brush options seem to make for good solutions either.
I experimented just now with a Type on a Path method using Dingbat arrowheads. (I used Zapf Dingbats.) It works quite well on smooth curves.
By giving the type a negative vertical shift (so that it centres vertically on the stroke) the spacing gets even better than this.
You can also use kerning and tracking for fine adjustments.