I agree with you, basically, but I do think Chaplains can shine - and even the score - with a less-than-stellar melee unit. Take tactical terminators. They suffer - at least a bit - from having a split purpose, with powerful power fists and decent durability, but not quite as much durability as hammernators. I wonder if the chaplain isn't a good fit for these guys because they need, more so than hammernators, to win that fight in round one.