Long term charm fits in that same grove as insta-kills - one die roll puts you out of commission - and that isn't fun, whether you're the charmer or the charmee.
However, WotC has reintroduced some effects that were previously 'insta-kills' as non-insta kill effects. The same can be done with Charms.
Example:
Charm Person Wizard Attack 1
Daily * Arcane, Charm, Implement
Standard Action Range 5
Target: One Creature
Attack: Intelligence vs Will
Hit: Target may not make an attack that includes you as a target (save ends).
Special: If the target fails 2 saving throws against this power, the target believes that you are his closest ally, and will treat you as he would his closest ally (no save). This effect ends upon the completion of an extended rest by the target.
It takes at least three rounds (or at least 3 rolls of the dice) before the combatant is really 'charmed', which prevents the combat from being over instantly, and the overall chance of success is very low unless you can give them save penalties (if the initial attack had a 50% chance of hitting, the chance of a successful charm is only ~ 10%.
It still has a lot of the interpretation issues old charm spells did, and the language can certainly be cleaned up, but the core concept could be used to implement charm and domination type effects. Honestly, I think we'll see something in this vein when we see psionics introduced.