1740573:actually, card that let you 'play' an extra major hero WILL let you play two armulet in a round... card that let you 'Put' a hero into play will not...
This is only half true.
LeBlanche creates a continous modifier that allows you to play an extra major hero any time during this round. Bring in the Big Guns creates a one-shot modifier that lets you put a hero into play immediately.
If ever there were a card that created a one-shot modifier (like Bring in the Big Guns) having you "play" a hero card, then you could still only play hero cards and not Amulets or Actions.
The important difference is not the words "play"/"put", but rather the modifier's type. LeBlanche somehow sets a condition in which you may play additional heroes for a specific duration while Bring in the Big Guns has you play a hero right now.