Hi!
Ability Focus is a Feat increasing the DC for any special attack by +2. As Channel Energy can do damage, it is an attack. Thus, Ability Focus (Channel Energy) should be possible.
From a balancing standpoint, I'd say that's okay. However, this duplicates Improved Turning, which does exactly the same.
This has four possible consequences:
- Remove Improved Turning; a reference to Ability Focus might be good, then.
or
- Forbid Ability Focus (Channel Energy).
or
- Allow both to be bought. A clarification might be wise.
or
- Change the effect of Improved Turning (+1d6 heal/dmg, for example), as there already is a Feat to increase its DC.