Dragon Age: Inquisition has a Nightmare difficulty mode available for players that want a big challenge. You may want to hold off recruiting Sera until after In Hushed Whispers. To catch them, walk up behind them slowly and then dash at the last moment.
Head up to the next Eluvian where you'll have to fight two agents and two spearmen. The first thing you need to do is reach The Broken Seal to the south east. The recommended minimum starting level is 20. You can also access the loot container which contains the ARROWWOOD bow.
