yeah, I always found that to be a bit "meh", too. I think there should be a rule that says "if you try to download from a source but can´t, your opponent may look through that resource and verify you can´t".
Currently,such a rule is only in place for mandatory downloads.
Apart from that, there is only this:
If you attempt a download using a resource such as your card draw and the download is invalid because no target card is available, you may not attempt to use that download again unless a downloading source is replenished (discard pile regenerated into the draw deck) or reopened (a closed Q’s Tent).
Discarding Q the Referee seems to be "using a resource", so if in this game at any time you attempted to download a
card from your draw deck, it seems you may not do so again until your draw deck is replenished - even if there were no
cards in your discard pile.
<edit: again, sorry to say the picture doesnt work for me. I dont know if there are more artillery shots in this episode, but the original image just is perfect for this card.
As to Artillery vs. Armus:
With the amount of Interrupts and Incidents in decks nowadays, there are, I guess, 50/50 chances that you will get a non-personnel card. IF you do, you will probably kill 3-5 guys (GREAT!). If you dont, you will kill 1 (BAD!). It doesnt stop the away team, so they will continue. With no built-in wall you need a wall before that. And with 1 bad probe you have wasted 2 dilemmas (wall and killer), which very well can cost you the game.
Armus will always kill 2 AND you can discard the related Event to seed an additional Armus dilemma somewhere. So: Armus, as fun as it sounds, is much more reliable.