It's...still a drawback. Atonement heals going to people that don't really need them.
Smart heals aren't always the smartest thing to use.
If the argument is that "Atonement is almost always the best thing to use," and a situation arises where it isn't...that's a drawback.
draw·back
noun \ˈdrȯ-ˌbak\
: an objectionable feature : disadvantage
The *disadvantage* to "smart heals" is they don't always go to the targets you want them to.
(oh, and just because people love to argue:
dis·ad·van·tage
noun \ˌdis-əd-ˈvan-tij\
a : an unfavorable, inferior, or prejudicial condition)
If heal A is *ever* a better option to heal B, heal B is disadvantaged in that situation.
But hey, I'm just arguing semantics at this point to see how far you'll go.
Atonement has drawbacks and limitations; some brought up that I haven't mentioned (needing hostile targets), and ONE in particular that none of the hardcore Atonement bashers have touched (aka healing the casting Priest for 50%).
Note: I'm still not arguing in favor of Atonement, I'm just saying don't say it doesn't have drawbacks (because then it WOULD be the smartest choice, always).