Well, on the other side, you can use several buffing skills on one creature. Like Momentum + Blessing. Why not buff skeletons and liches a little more? Death has no buffs at all.
This card is intended to work in synergy with the Nightfall and Boneyard
Does blessing have synergy with blessing? No, it is redundant.
Would a card that gave skeletons a skill have synergy with Nightfall? Yes, depending on the skill.
Momentum (Skill) + Blessing (Stat buff) = Synergy
Momentum (Skill) + Momentum (Skill) =/= Synergy
Blessing (Stat buff) + Blessing (Stat buff) =/= Synergy