Are poetic contractions, such as "e'er", "o'er" and "ne'er" (and other less common ones), English? As in officially recognized?
I'm not sure what it means to be "officially recognized" in English; there is no official list of English words.
If you mean appearing in dictionaries, then yes, it is a word.
(If you mean being employed in speech or everyday writing without sounding odd, then probably not. Its use is restricted to poetry, as you acknowledge.)
These contractions are primarily relegated to literary usage nowadays, and such usage is sparing in modern literature.
There is one phrase, however, which enjoys continued popularity in the spoken vernacular:
Some might call it vestigial, but unlike the appendix, it still serves a useful purpose. No synonym carries the freight of implied prescience that this term bears.
"Wastrel" rolls deliciously on the tongue, and "good-for-nothing" judges those who are by present accounting utterly useless. But only "ne'er-do-well" pronounces "I have seen into your future, and there is no hope for you."
Yes, they're real abbreviated English words, though I wouldn't use them unless I wanted to sound old-fashioned or poetic.
What do you mean officially recognised? English has no official arbitrator other than your dictionary of choice; so just check in your favourite dictionary!