exp chain is sustained when you kill a monster that is equal to or higher than your level within the timeframe - it is independent ofnthe type of monster you have to kill.

also, dungeons do give quite a bit of exp if you have rested exp bonus, and armoury exp bonus. in brayflox and with bonus, 1000 per kill is normal. it gets to around 1.5k at temple of qarn and cutter's cry, and gets to around 2k beginning from stone vigil.