While I agree the feat is definitely worth having because it makes life so much easier, it isn't completely necessary, even for a battle healer.
As a few examples:
Party takes on a single dragon. If the cleric takes a few steps in the right direction, they should be able to channel getting most of the party without getting the dragon in the radius. Even if the cleric has to get the dragon inside the radius, it may still be worth healing the dragon if it allows the rest of the party to sustain damage output at a higher level.
Party takes on a horde of monsters that take one hit to drop. Because healing caps out at your maximum health, the channelling won't have any noticable effect on the monsters. Either they're healthy or dead.
Party 1 takes on party 2 where party 2 has selective channeling. After party 2's cleric has channeled, the cleric of party 1 may want to risk a channeling if the benefit he supplies his enemies is minimal. In the examples you gave, I would consider having the cleric hold his action for after the other cleric and before his next party member's turn. That way he doesn't have to worry about healing any extra damage and rendering another party member's turn worthless.
Personally, I'll still be taking the feat as I wouldn't have to think as hard about the tactics or moving into the right spot. I also agree there aren't many better choices at first level for a cleric, I just wanted to point out that a cleric can still function without it.