You cannot start with 3 power pips in PvE. I'm guessing that you saw this happen when you joined a battle late. If you were standing there in the battle but missed first round, they passed or cast a 0 pip spell, when you started they had 3 power pips. But it was second round for them. The upcoming Khrysalis part 2 update has decks that add another pip, but it is a regular white pip not power.
As you most likely know, there are some wands that give plus one pip at the beginning of a battle. Some extremely rare wands, my brother has one, give you plus 2 pips. I am not sure about this but there might be some gear as well. Do not worry, they weren't hackers, just lucky people