Discipline versus Ancestor's Echo

Just thought I'd post some quick numerical analysis and thoughts on two talents: Discipline and Ancestor's Echo.

At 30% crit, 13 Grugni/11 Grimnir, Average Heals (including crit):

Ability	1050 Willpower	890 Willpower (-Discipline)	Diff	25% Ancestor's Echo
Rune of Regeneration	2812	2646	-166	+0
Grungni's Gift	707	652	-55	+162
Blessing of Valaya	7734	7071	-663	+972
Rune of Serenity	6333	6002	-331	+0

Benefits to Ancestor's Echo:
Doesn't overheal - more useful when casting Blessing of Valaya for non-damaged party members.
Ignores heal debuffs.
Worthwhile when you reach willpower cap without Discipline.

Disadvantages:
Actual value is less powerful than a raw heal because shields ignore resists and armour. 100 HP lasts a lot longer on a tank than a 100 point shield.
Doesn't affect Rune of Regeneration, Rune of Serenity, Rune of Shielding.
Unaffected by Blessing of Grungni.
Less reliable, but still a good proc rate.
Could spend 1 mastery point elsewhere.

I believe the disadvantages indicated in italics probably don't initially occur to people when thinking about the tactic. Do people think it is more viable than Discipline when you aren't willpower capped? Comments please!