I would recommend you (and I am not impartial) to try Guild Wars 2.
The mechanics of the game are designed around empowering players to play the game rather than wasting time on time sinks.
Hundreds of Waypoints that, after reached by foot for the 1st time, you can teleport to immediatly allow for not wasting time when making groups.
Downleveling keeps low level zones and dungeons interesting for higher level players so they are not depleted. You will still find less people in low level zones or dungeons than after game lauch but it is not as bad as in other MMOs.
No lockouts that stop you from playing what you want. No complicated prerrequisites. And if there is a prerrequisite (like beating this dungeon in story mode before doing explore mod) it is enough if one member of the group has it completed. The rest in the group can also do and get credit for it if succesfully completed.
And, most important of all, it is designed around the idea of player cooperation. In other games you go with all your good will to help someone and you get angry messages about "stealing their mob". Or the people who think the mining points are their property and scowl at you. In GW2 mining a point gets you your items but all other players can still mine that same point once per day. Damaging a mob will net you XP or items but so will do for the other ones helping even if not in the same group and without a disminution of the reward for not doing 100% damage. You get XP for rezzing people, and all classes can rezz.
Which means that in GW2 the usual player, even the younger ones, are kind and helpful. We still have trolls, but way less.
Oh, and there is no monthly fees. Just the price for the box/serial key, like in offline games. They have a microtransactions shop, but with no I-WIN or even I-ADVANTAGE items.
Hmmmm, should I apply for the GW2 marketing department?