[Edi]

It's probably an unintended side effect of the bless effect, so it can be considered a bug, but I do not know if there is any way to actually fix this.

What happens with blessed F9/D9 troops is that their weapons get a secondaryeffect of either "bless fire" or "bless death", which are both weapons. It is probable that the bless secondaryeffect overwrites the aoe secondaryeffect, since you can only have either secondaryeffect (takes effect on hit) or secondaryeffectalways (happens no matter what, which is what aoe effects are). So the bless effect is added, weapon has a secondaryeffect and the secondaryeffectalways is disabled.

That's my reading of it anyway, but I need to ask Johan to look at it.