Rift does have multiple modes for most instances - Normal (tuned for a level between 15 and 48, mostly), Expert (which is tuned for level 50), and Master (which is tuned for well geared 50). The Expert mode generally extends the Normal instance in some way - additional bosses, new mechanics in the existing fights, that type of thing. The two Master Mode instances are different beasts - MMDD is just one more boss (above the Expert mode), while the MMCR is the combination of two Expert mode dungeons (Upper and Lower Caduceus Rise), with a few additional wandering bosses tossed in the mix.
Also, there are leaderboards, but no rewards or normalized gear. All about getting the best number for the week in different pools.