Lots of grouping, most efficient method of levelling is group. Also, dungeons are tied into story quest so mandatory, as well as a few random boss battles from 1-50 that are mandatory as well, group.
There is a trinity in a sense... every group of course wants tank healer and at endgame you build your 8mans 2x tanks 2x healers and at least 1 bard, then the rest of the 3 slots based on your dps synergy that your looking for, usually 1 melee 2 blm.
CC isn't important unless you are using it to skip trash or do speedruns, later on theres quite the niche for train pulling and cc to help clear the current farming dungeon quicker.
The dungeons are a numerous amount 1-50, but then at 50 there is basically only 2, right now it is severely lacking group content at 50 that isn't 8man. There are 2 4man dungeons, 3 8man primals and then binding coil which is the 'raid zone'. All the dungeons are linear at 50. Though the tedium seems to be broken by taking a 45 minute dungeon and clearing it in 9 minutes through gear/trains/cc.