Undying Evangelist: increased or reduced duration?

As any summoner who has ever used evangelists know how slow their kills are due to the "delayed" aoe blast they do, spell echo helps this but still there are now double "delayed" blasts lol. So I am asking does increased duration and reduced duration affect the delay of the blast? I mean I have always ran my evangelists with at least increased area of effect and increased duration, spell echo was an add on at its release.