But again, that's where the beauty of playing a multiplayer online game comes in. They are not left in the dark completely. They can easily make friends in game, and ask questions. "Hey man, what do you think I should use?". You're right, it is confusing for a new player to MMO's, I've said that before, but they are able to easily do their own research, look at their talent set up(such as a talent that states something like "X strike deals 10% more damage") and they will decide to use X strike over Y strike because they are gaining more benefit for it.
More detailed example, when I first started as a Cleric, I had Sentinel/Purifier/Warden as my choices. I had 2 carbon copy ranged spells. Both 2 second casts, dealt the same damage. However, two points into Sentinel caused the Sentinels version to snare the target. I dropped the Purifier version and picked up that. When I respecced to Shaman/Justicar/Druid, shaman gave me a buff for 5% extra physical damage. So, naturally I didn't use the druid's elemental strike version of the same strike shaman gets, because shamans was physical. I just used the non-striky stuff of druid(the shield, and the pet). I wasn't new to MMO's no, but I was new to Rift, and I could figure it out within the time before I even started doing grouped dungeons. It wasn't exactly difficult to figure out after looking at my options.
Minecraft didn't tell you what you needed/should do. People figured it out, figured out recipes, and made guides for those who don't want to spend the time figuring it out. Rift will be no different.