On paper Act 2 Merc with Infinity (and other aura) would probably increase your chance to hit more than Act 2 with Blessed Aim.
I saw people using Act 3 Merc to trigger Enchant. But I think it is used for Ubers only (where the Merc will end up dying). Or else a Act 2 Merc with Blessed Aim will give almost the same AR, or even more AR if you add add level 21/22 Enchant (from Obedience/ Demon Limb).
When I thought about a "Elemental Attack Paladin" that self use Conviction ( Vengeance or Dream or Dragon + Hand of Justice), I thought about using Act 2 Merc with Blessed Aim
fredkid
884