Various opinions on this sorta thing and also bare in mind each person can have different tastes on what they do and dont like to be buffed with.

Not using Ewer on a BLM is typically correct as it can mess things up; only in rare circumstances and something that has been pre-coordinated would this ever be used tbh.
Ewers are a good use on BRD' who use songs like Foes as it lets them do so longer. Otherwise self use usually, or a very rare PLD who messes up.

Never tbh heard of "dont use spear on NIN", i mean generally spear is semi-useful for anyone; sure some people wont see the point because they use cooldowns at specific times so it doesnt matter if it comes back up early but then, well if you do get speared no one is forcing you to use things earlier so. Personally i find Spear to be SMN/Healer/Tank bait if i have to use it

If it was The Arrow on NIN id understand, in general content it may be fine but for higher stuff i think generally a lot if not all melee dont like Arrow due to TP floor.
Never had a view point from BRD/MCH about Arrow so idk.
Typically BLM will like Arrow, maybe certain circumstances where they wont want more speed but idk them.
Generally wasted on SMN ive found, sure it works but wont change much.

and ofc balance is EVERYONE
also unless its changed, hitting everyone even in 4man duties with an aoe balance > enhanced or extended on a single person
unless you have on in spread and draw another
then your laughing



as always i could be wrong about stuff and this is partial opinion/what ive found so