Mage Secret Duplicate interaction with AoE damage [duplicate]

The secret will give the mage two copies of the minion that dies first.

The order in which they die is determined by the order in which they were played. So if the opponent dropped his other minions before Dr Boom, then one of them will get duplicated; if he dropped Dr Boom first, then it will be duplicated.

The Boom Bots that are summoned with Dr Boom are "played" part of his Battlecry effect, so (if they're still alive when you use Consecration) they will die after him in your scenario.

The Duplicate gamepedia page also has a note on this:

When multiple friendly minions are killed simultaneously, Duplicate will copy the minion that was put into play earliest.