Yuka Pontasu-sama
This is Kawaguchi Hidetoshi. This is my humble answer to the question.
The “Heart Sutra” deals with important contents for understanding the “sky” in “wisdom” out of “wisdom and blessing,” which are the two materials that should be practiced for “enlightenment and nirvana,” which is the purpose of Buddhism.
It's just my personal opinion, but in the Jodo Shinshu, who places emphasis on Amida Nyorai's “death” to paradise, I understand that even though the “Heart Sutra” (content) is unnecessary for “past death” (or interferes with death, or acts on one's own power, and furthermore, it is a magic that should be denied by Jodo Shinshu), it is probably necessary in order to reach “enlightenment and nirvana,” which is the ultimate goal. I will.
Well, even if you don't deal with it in this world, in any case, I think that after passing away in paradise, you will also practice the contents of the “Heart Sutra” due to indoctrination by Amida Nyorai.
Certainly, rather than half-heartedly aiming to understand the true nature of the “Heart Sutra,” if you are directly receiving the indoctrination of Amida Nyorai in paradise, you will come close to complete understanding, so of course, prioritizing “death” over anything else is of course not incomprehensible...
Anyway, the content of the “Heart Sutra” is definitely essential for “enlightenment and nirvana,” so I would like to endeavor to understand it as much as possible in order to improve “wisdom.”
Now, as an answer to your question, I think turning the merits of chanting the “Heart Sutra” to those who have passed away (not only so that all sentient beings are saved) is important as something that contributes to wisdom and good fortune for those who have died (not only all sentient beings) to reach enlightenment and nirvana.
So, in my humble opinion, I don't think there's a problem.
Also, when it comes to the Heart Sutra, along with reciting it, it is necessary above all else to understand its contents. I would be grateful if you could also refer to the following humble remarks.
“On the 'sky' in the Heart Sutra”
http://blog.goo.ne.jp/hidetoshi-k/e/93cd51b49c2264eb00fcc00a904a3392
Kawaguchi Hidetoshi Gassho