To your question on chanters, they do not lose any functionality at high levels and are equally, if not more, critical to group success. Slow does become more difficult to land, but that is the lesser of an enchanter's roles. No class ever comes remotely close to machine an enchanter's crowd control ability (their role) and their mana regen/ haste buffs are unparalleled.
Nay, an enchanter's desirability for groups/raids does not wane ^^
|