It's not as easy as D3 I'd say, and you can change difficulties at certain levels (like world tier 3 at lvl 50) and from there also start doing nightmare dungeons which are the same dungeons based on your world tier but have random abilities or monsters that do certain things for that specific run. More rewarding both in xp and loot but way harder, especially if you running hardcore and can't risk checking if it's too difficult or not at times.
That said a lot of people are complaining that leveling past 60-80 or so takes way, way too long. People spending 8h to get a couple levels past 80 or so.