Return of Reckoning

As the titel says, what is more needed in a WB or better useabel to hit the enemy? 25% longer cast time or 25% heal reduce?
Yeah i know, in org. Is good to have both. But if you need to chose one, wich one you get or is better, worses for the enemy wb?

If you want to disrupt the enemy's combat rhythm, especially casters and healers, increasing cast time by 25% is a top priority. It affects everything, not only healing but also buffing, control, and attacking.tunnel rush

Cast-time increase primarily affects enemy healers negatively. Mdps and tanks are largely unaffected by it.

As you said, ideally you want both. And indeed, after rr70 you can easily fit both in your SnB build (and use both if needed). Since most Chosens will prioritize getting the Heal Debuff aura, it may be wise to spec the cast-time increase aura. On the other hand, it requires you to play closer to the enemy backline, which you can do most comfortably at BIS. Finally, if you find yourself being the only Chosen in a warband, you would ideally want to have the heal debuff aura and not the cast-time increase one.

It's your choice at the end (but you won't have to think about it too much in organized warbands or after rr70)

If any, than build up time. Heal debuff should come from different sources in organised group play. Also you should rarely run into the occasion to switch of ap/str/res or ap/tough/res