My point about the ability to see whether the source text uses end-rhyme (or internal rhyme for that matter) is that the reader of the translated poem than then judge more accurately what has been sacrificed, and what has been ‘reproduced’ in the target language. Of course, the same applies to some rhetorical ‘schemes’ as well: parallelism, for example (so common in Chinese classical poetry). Has some attempt to replicate this been made, or has it been sacrificed (perhaps for very good reasons)?
It’s true that many modern translators avoid end-rhyme, for the very good reason that when one concentrates too hard on achieving end-rhyme (fun though this can be), the meaning inevitably gets more and more distorted, though the form may be retained. However, the fact remains that end-rhymed verse in some languages translates more efficiently into English than others.
The trouble with Chinese classical verse is that Chinese, whether ancient, medieval or modern (the former two being largely monosyllabic), contains so many more rhyming ‘finals’ than does English, that the distortion becomes that much greater: look at the far from pedestrian though now almost unreadable work of Herbert Giles. However, a tiny handful of modern translators have managed to overcome this problem: Vikram Seth in our own time, or Ayling and Mackintosh a few decades earlier showed how this could be done. What’s more, European and Russian verse from earlier centuries often cries out for end-rhyme: think of Petrarch, Ariosto, Tasso, Gongora, Ronsard, Pushkin: the form being such an important component of the meaning. My own practice (for what it’s worth) is to use end-rhyme whenever it suggests itself, provided the semantic distortion is kept to a minimum.
You’re right about calligraphy being something that really does get lost in translation: Chinese poets were very often just as famous for their painting and calligraphy as they were for their poetry, and very frequently one can’t easily dissociate the calligraphy (or the calligraphic style chosen) from the poem itself—to give one example, in a particular poem by Du Fu about a night-scene beside the lake, there’s a preponderance of characters containing the ‘water’ radical, which is immediately apparent to the reader of Chinese, but which is hard to reproduce in any translation; and in another, more famous poem by Wang Wei, describing blossom slowly opening the five characters in that first line slowly unfurl and exfoliate as the flowers emerge: an effect impossible to mimic in English.