Some of these may be already suggested by others:

In PVE:

=Players' attacks when fighting with mobs should be targeted to mobs just in case if there are crates or barrels around. Because right now, if I use a skill, the skill will target the crates/barrels and not the mobs.

=Fix the loot system of the game because some epic items are much harder to loot than legendary (for example Nexus). Common>Rare>Epic>Legendary it should follow that system where Legendary is the rarest. No problem with Mythics and Arcane because they are fine as they are now. Also if there should be an egg that will loot in a chest, its rarity should also define how hard can it be looted properly.

In PVP:

=The invulnerability shield should be disappeared after the player step out of the spawn area.

=We should able to chat even if we die. (Especially to mobile users)

=(This one might be insane. but) There should be a system where a player can declare a versus with others, where the latter can accept or decline the invitation. If the player accepted the versus invitation, the system will announce it to other players. And if the versus is on, any players that are not included to the fight and attacks a player that is on a vs with another, will die instantly (Just like when you die when you are stabbed by sword gates in planar arena) to prevent any interruptions and unfair death. This will prevent a player being on a disadvantage side because there will be no outer force that will kill him aside from his opponent on which he declared his vs on. The vs can be any number like 2v2, 1v1, 3v3 and even 2v1, 3v2, 4v1 if thats what they have decided on. They could just decline if they dont want to. I guess this should be only applicable on CTF because in TDM it should be team play.

=There should be a message and a voice saying you performed a killing spree because of your kills in a row. (For example, Double Kill, Triple kill, Multi Kill)

=Your kills in PVP should be rewarded with XP

=The winning team at the end of the game (TDM only) should be granted a prize like gold, items, vanity, and etc. That is if one of the two teams really scored 20, so to prevent a team on having an easy win by just getting a few kills where the other just gave up and leave. So the game should end with a team having a score of 20 kills.

=The chats in pvp should have corresponding color like Blue for the blue team and red for red team. This should be easy for players to identify what team he/she is on.

=In TDM and in CTF, there should be an icon "Create Room" to provide rooms to players who want to fight with their friend, guildies, or even guild wars can be implemented by this. They Create Room by providing a room name and whenever players will do "/room <name of room>" they will soon be joining that room. So for example, Unified want to have a war with Magnum, the two guilds should decide who will create the room and the name of the room, so they can all have their own designated pvp map. Because of this, no one will interrupt if there is a tourney going on or friendly fights in pvp.

Problem I found in Sorcerers:

=They have a second delay when firing a gun and casting a spell like Lightning, Ice, Fireball, SHield, and Clock. Unlike the sorcerer, the rouge and warriors can easily cast the spell or shoot out the arrows without any second delays. I hope this can be fixed with a lot faster animation. For example, i am a mage and i fire a gun, the bullet should be out already right after i release my finger. There should be no second delays. I dont know to the other class, maybe they are facing the same problem also.

That is all!! Just comment about what you think and you can improve my ideas just make sure that the developers can know about this so we can alll have the best game experience.