I think it should cost $5 or $6. And it encourages money strategies, which are never fun.
If it encourages boring strategies too much, the solution is not to weaken the card, but to not make it at all. But whether it really encourages money strategies remains to be seen.
I just realized something wrong with this card. According to Adventures rules, "immediately after resolving an Action" only counts its on-play effect if said Action is a Duration; its next-turn effect doesn't count as resolving it. So, as worded, all Duration effects except those from playing it the first turn are completely unaffected by Warlord's attack! Here's how I would fix it:
Why does this need to be fixed at all? It's totally fine that Duration effects don't trigger the attack again.
Hmm... Here's an idea: Have it trigger it at the start of the respective player's buy phase. Less fiddely, but of course you get to play your whole turn before discarding. I wonder whether down to 4 would be too harsh, and whether that's worse for BM or engines.
There was an Adventures outtake that did just that.
Raider: Action–Attack–Duration, $4
At the start of each other player's next Buy phase, he discards down to 3 cards in hand. At the start of your next turn, +2 Cards.
It was too weak. So no, discarding down to 4 is not too harsh at all; it's not harsh enough.
Hmm... Here's an idea: Have it trigger it at the start of the respective player's buy phase. Less fiddely, but of course you get to play your whole turn before discarding. I wonder whether down to 4 would be too harsh, and whether that's worse for BM or engines.
I think that down to 5 would be too dependent on the board (only useful against cards that give +2 or more cards), but 4 seems good. I would price that at $5 instead of $4, assuming the self-bonus is the same.
Yes, good point. I think if I were to test a version, it would make each other player discard down to 4 cards in hand after resolving each Action. Maybe it would be too anti-engine in practice, but I think it's worth a try to see how it really plays out.