When a mage with the Deepwood Sphere casts the damage causing version of tree-singing, can he re-roll:

a) the die to see how many hits that the unit takes
or b ) the rolls to wound in addition to the D6 for how many hits the unit takes.

I think it's the former, but I don't know. Anyone's views will be appreciated.

It is the former.

Re-rolling the number of hits given rather than wounding, as is the norm for similarly worded effects. It would specify rolls to wound otherwise.

That's what I thought, though it is a badly worded item in my opinion (like lots of gamesworkshops rules, but oh well).

That's how I interpret the deepwood sphere. Also remember (and I'm sure you already do) that you can also re-roll the distance when determining how far a forest moves.

~ Lindsay ~