+1 for shove being an action. In my case, I find it annoying how it weakens Sleep.
And the examples given by OP show how it's pretty unbalanced.
Furthermore, I find that this tactic of shoving is way overused by the NPCs. It would be nice if it didn't trigger that often.
I don't like the sleep argument, sleep is already one if not the most powerful CC spell in the game. An AoE loss of action for multiple enemies without a skill check, that guarantees a crit, all that packed in a level 1 spell is already silly enough.