When wax has been melted and reapplied over and over again, it can turn into fragile resin. This makes the edges of a Waxer sharper and more dangerous, but much more brittle.
Wickstone is effective on units who have the Burnout affix (assuming that it would be advantageous for the unit to live longer, which isn't always true). The +1 Burnout doubles the life time of the Draff, the +5 bonus is effectively doubled with Multistrike, and the +5 bonus helps against units with Sweep.
Alternately, Immortalstone is effective on units with low Burnout values. The Draff is cheap and only occupies one Capacity, so it could absorb a hit for your front line unit or deal its decent default damage to the front line enemy unit.