that's great to hear (that you played the game a lot, not that you found a bug :D).
No, the archer is supposed to work whenever it's on top of the pile, no matter whether it has cards under it. Its bonus is calculated at the start of the round so it doesn't account for destroyed cards (by technical/time limitation, not design tho). I did notice it being a little inconsistent though, but only after the deadline unfortunately.
Oh well - it's a GameJam game, here be bugs. :D