There are many Encounters which intend to have "mechanics" like a boss-encounter in other games. Some might be easier, if you get them.
LvL5 is a milestone-cap (AOE DMG/HASTE/2nd attacks etc) try to get that level by exploring, doing side-things etc.
I feel underleveled at lvl 8/9 at Baldur's Gate by now, because my party encounters lvl 11-13 enemies - just ridiculous.
