Downloaded this to give it a shot since it's going F2P...
How relevant are the difficulty rankings for classes? Lancer looks like the coolest class but it has a high difficulty rating. Should I pick an easier class to learn the ropes of the game and then switch to Lancer? I'll probably be using a controller (but I can switch to kb/m if controller is useless).
Oh man, if you want to see a good time you should ask this in global chat in game
But to be serious, they are not really that meaningful, in a sense? They are more like estimations of the amount of attention you need to pay to play the job well in a group setting, I guess? Or an indication of how flexible the class is. I would just say ignore them, honestly. Like, leveling as lancer is super easy because you're so tough, so in that sense it's like 1 star difficulty. However, in a dungeon, tanking as a lancer can be pretty challenging--way more than, say, playing a sorc.
Different classes need to rev up different skills in group settings that they don't use as much or at all in solo play. For example, a good lancer is not just going to hold block and hit shouts (taunts); you need to be doing your own damage skill rotations and maintaining debuffs on the boss while reducing incoming damage to manageable levels without losing hate (learning to read enemy attacks and knowing how to time blocks)
and maintaining awareness of your surroundings (WALL DRILLS CRAB BATTLE) and your party members positioning. This may sound like standard MMO tanking requirements, but the active combat system makes late game encounters (especially hard modes) challenging to multitask in. Meanwhile, your slayer and sorcerers are mainly just going to be focused on doing a skill rotation for as much DPS as they can with much less attention needed to be paid to certain factors.
tl;dr don't let the star ratings deter you, but be aware of what the class's role actually is (as in, don't pick a lancer and expect to be a damage dealer).