Like Captain K mentioned, I believe it all comes down to build, and with the cleric there are several viable alternate builds just with the base cleric.
A cleric that is focused on spellcasting is likely to stay at range, so they aren't going to see a lot of value in HAP.
A cleric focused on archery is also likely to stay at range, and therefore is just as unlikely to see much benefit from HAP.
A melee-oriented cleric, however, will see substantial benefit from HAP. Naturally, they will have to give up something else to get this benefit, but that's how feats work. You choose one benefit over another. And for the melee cleric, HAP is a fair option.
In my current group, we have two combat clerics, which my magus refers to as the Twin Towers. They both wield heavy shields and one of them has HAP and an AC of 26 at 4th-level (I think the other is also planning to eventually pick it up, but am not sure she has at this point.) As we have no paladin or fighter, they're usually our front line and a high AC is a definite plus.