Unique idea for new league to help new players play build they want instead of necessary metas

Group / Raid league
introduce a new gem slot for "roles"
IE; Tank, DPS, Ranged, Spell, etc
This gem would level with you as you play the role allowing you to slot in more support gems as you progress with the role
IE; Tank gem would get things like intimidate, damage resistance, etc.

Introduce new world bosses that require group mechanics as well as multi boss maps that also require group mechanics

This would allow people to play builds the way they want without having to follow meta builds (Herald, autobomber, etc) with a fully rounded out party, you could have your dps and support characters while one or two are taking care of DPS. Make tanks / armour viable so you can have someone taunting and holding aggro while the support and dps builds are focusing on dishing out as much damage as they can. Allow pathfinder type builds to focus on healing, minion builds focus on buffing etc.