User blog comment:Jibojie/Dragon's Roar Deck (Dragon world)/@comment-1755882-20140120210639/@comment-11454852-20140120211032

There's an advantage on using 2 copies of 2 cards instead of 4 copies of 1 card though, it gives the deck more flexibility, but I agree on sticking with 1 Impact though, both are finishers so you only need 1 per game, so the other copies become Gauge fodder.