[Blizzard's readme doesn't] mention that having the Sanctuary aura up apparently grants your melee and ranged attacks the ability to ignore undead resistance to physical completely.

In other words, in some situations, Sanctuary is a "one point wonder."

...an Assassin could grant themselves the Whirlwind skill without having to use the runeworded claw to WW with (instead using an elite polearm, etc.). Another example: a party of exploiters could "pass the roach", giving each player some special skill from an uber item even though none of them was still using/equiping it.

If the xp you see your hireling get when you make a kill is at or nearly at the "cap/3" number then you know you're doing as well as you reasonably can. If instead it is a lot below that number, you should consider finding more suitable prey.