Question about Warrior mechanics
Cards are always played and resolved one at a time, so your opponents will discard (and potentially trash) a total of 3 cards.

The specific sequence of events:


Play a Village


Draw 1 card
Add 2 to the number of actions you can play this turn

Play a Warrior 


There is 1 Traveller in play (the one you just played), so each other player discard the top card of their deck and trashes it if it costs $3 or $4.

Play another Warrior


There are 2 Travellers in play, so each other player does this twice: discards the top card of their deck and trashes it if it costs $3 or $4.



The first Warrior will be completely done with everything it does (except being exchanged when discarded) before anything in the game knows you are going to play a second Warrior.