Which unique secondary skills are best for heroes?

Hmm, it seems most haven't played the expansion pack enough yet. All three of the dwarves' abilities are very strong, especially the updated rune, which allows you to cast the same rune up to four times on a single stack (and if it's an area attack on Jarls and Godzillas, that's 8!).

Demons have a very good Hellfire spell because it doesn't depend on the number of units in the squad; you can even use a single unit to deal significant damage and negate retaliation.

The Warlock has three very worthwhile abilities...

The Academy has the Wizard's Sign and Magic Mirror... but the artifact absorption, even considering the unit restoration in the squad after absorbing an artifact, still doesn't impress me too much.