Was thinking about this for a while so I thought id write it down.
Skills : I would unbind skills from weapons and classes, but keeping Elite skills linked to their profession. this would mean for example a warrior could take a rangers pet and say some guardian skills. skills would still depend on use of weapon but wouldn’t be bound to the skill bar, for example barrage would be useable only with a bow, but using a bow, wouldn’t auto fill your bar with skills.
Henchmen: since GW2 is more open than GW1 maps you cant really do the full party thing when roaming, BUT having one henchmen when questing ect would work, you could level him/her up give a small talent tree too, maybe expand it to max party size when in dungeons depending on AI.
Signet of capture: I would put in alot more skills (PvE only as they seem to balance it off Wpvp) so you would have to go hunt down a unique named boss with your professions aura, granting you either a normal skill or a new Elite spell like spitefull spirit for nerco’s
Unique bosses : this sort of ties in with Signet of capture but have named bosses or unique model bosses that drop unique weapons/skins still RNG based but you know they can drop something cool.
Solo challenge: id like to see some solo challenge modes/dungeons, GW1 had a few the drunk dwarf one springs to mind, one easy way would be to scale dungeons down, but scaling loot down also so its not better or worst than doing it with a full party
Factions: not the expac but use of the 3 factions more: picking these atm does nothing but say’s who dies mid game, how about attaching quests or events to these factions example order of wishpers sends you out to assassinate a target that randomly spawns and you have to track it down.
Housing: yes we have one sort off, but it isn’t being used to the max, why not treat this like the old HoM in GW1 store armor sets trophies mini pets ect being able to hire NPC to work say on gathering nodes for a fee.