This one is probably simple enough not to need a background explanation
Q: If the Overlord uses the 'Focused' upgrade to send a Power card (such as DOOM!) to the Graveyard, do Lieutenants who 'have' that power still place the card in play during their battles and when fortifying nearby dungeons?
A1: No they do not; the card is out of play forever!
A2: They still get the benefit of the card, it is simply no longer in the Overlord deck.