Leaders riding with non transport units.

[Poor Yorek]

For example, a 2X hits a leader and reduced step.
Case 1 will have the leader survive as he was not alone when the 2X hit.
Case 2 will have the leader killed because the first X killed the step, leaving him 'lone' for the second X to be applied..
To be controversial, Wayne and I (and I think Alan) use case 2

Not that we vote for truth, but TheDoctor and I play "case 2". A leader and mortar (or gun) in a hex suffering a 2X result would both be eliminated. A leader and a two-step unit taking a 2X result would lose the unit; the leader would make a casualty check; then, should he survive; make an M2 morale check (and ask: "where'd everybody go?").