I definitely support using apostrophes to mark elided non-terminal vowels. As for blessed: I prefer it being written as blest (or bless'd if one considers the words to be somewhat different) if it's being sung in one syllable, as that's one -ed that enough people may pronounce out of relative familiarity with it - it's not fully archaic.

Basically, don't make it an unnecessary myst'ry for singers, whether choral or congregational. If you imagine everyone ought to know - your imagination is insufficient.

Though choral scores of yore used word divisions that were considered logical for singers, I am a firm believer in literacy, even in choir. Thus, my experience has brought me to the following conclusions:

- whether elided or not, "glorious", like "glory" receives the hyphen after the "o", not the "r"
- "oil", et al., are always one syllable (as is "lyre" further down the list); "chrism" is another matter, and I've decided the word should be dropped from the English language, at least when sung
- "desire" (like "fire", "mire", "entire", "conspire", etc.) is never divided in the "ire"
- "toward", unless you are a true archaic, is one syllable
- the two syllables of "lion" could probably take one note, but certainly not "Zion"
- "Jerusalem" is always and forever four syllables
- I've gone back and forth on "power", so good luck

Just, whatever you do, please don't divide "every" into three syllables, even elided ("ev-'ry"). It should be hyphenated "eve-ry": a stumbling block for singers, perhaps, but at least a nod toward literacy.

I often use the following for English text: https://juiciobrennan.com/hyphenator/

and this one for Latin text: http://gregorio-project.github.io/hyphen-la/

These are accurate 98% of the times that I use it. There are occasions when certain words need an elision.

Thanks to all- its good food for thought. Its been a discernment for us because we are trying to use Monastic Tones with the English Language- which can sound strange with certain accented words. Then put a community with Sisters from North South East West of the USA, Philippines, Mexico, Dominican Republic... et alia.... and not all of them sing, but all sing (if you know what I mean), then unity can tend to be problematic in the Divine Office... but these are all helpful insights.

In the Beatific Vision we will have the perfect liturgy!

Treat English like a beautiful language, and chant like chant, and all will be well.

Do you know, Sister, about a recording called The Highway Code, or one called Pigorian Chant?

https://www.youtube.com/watch?v=Qngi_jSaXlI


https://www.chantcafe.com/2012/10/pigorian-chant/

Here is a website that applies standard syllabification to English words that I use all the time: https://juiciobrennan.com/hyphenator/

It's actually rather important to use standard syllabification, whenever possible, as these are standard conventions that extend beyond liturgical music. Problems arise when deviating from the norm; it makes reading the music more difficult, and as we've discussed previously here on the forum, when you break from expected syllabification, this can cause singers to make mistakes that are otherwise easily avoided.

The exception to this rule is where composers / arrangers may use discretion with deliberate elisions. Ky-ri-e e-le-i-son vs. Ky-rie_e-lei-son. Both versions may be perfectly licit depending on how the text is set to music, but you'd still want to keep the syllabification as standard as possible.

As for "blessed", this is a word that is fraught with difficulties.

I employ the convention that changes it to "blest" when it is one syllable, as this prevents any confusion. As suggested above, "bless'd" works well also. That said, I prefer the older form, so I mark this with an accent to make it doubly clear as well: bless-èd (drawing from the French accent grave). I've never had any difficulties with blessèd when marked as such.

Now to the OP: your questions seem more about the composer/arranger side of things, so here's where I land on these:

GLO-RI-OUS & GLOR-IOUS
OIL / TOIL / SOIL (notoriously difficult, but better with an English accent than making them two syllables with a hard mid-western / southern accent!)
SANC-TU-AR-Y
DE-SIRE / FIRE
TOWARD
MYS-TER-Y
LI-ON / ZI-ON
JE-RU-SA-LEM
LYRE
VIC-TO-RI-OUS
VIC-TO-RY (VIC-T'RY is also common)
POW-ER & POWER (context)
SUF-FER-ING & SUFF-'RING

Some things are just context dependent and work in more than one way like the aforementioned Kyrie Eleison.

And NB: a few examples needed a letter shift like suff-er-ing to suf-fer-ing. The lyric hyphenator link at the top of this post will help with double checking stuff like this.