recommend Staff and Sword/Sword (or GS) for leveling in open pve. Why? Because the Staff is an excellent kiting weapon, especially for Champions when you want to solo them. When you combine the iSwordsman with Chaos Storm he also gets Chaos Armor because of his leap attack.
The illusions are weak at the beginning, especially without traits or the signet. Their main purpose is to grab the aggro, keeping the mobs away from you. The phantasms have a high cd and are killed within seconds, so better rely on clones who have a much lower cd. In general mobs will attack: Phantasms > Mesmer > Clones. If you have no clones summoned but phants only, the mobs much likely will attack you instead of the phants, because your attacks are much more frequent than the phant’s ones. To lose the aggro simply stop to do damage.
Mirror Images is great to start with (make sure to have the staff equipped when using Mirror Images, because staff clones do condition damage with bleeding and burning too), later I’d swap it for the Mantra of Resolve when mobs in higher level zones start to do more condition damage. I also recommend Signet of Inspiration to buff yourself every 10 seconds with a random boon.
Build until Level 79 inclusive:
2 – IV, complete Lornar’s Pass or buy it for 10 silver and 2 skill points
4 – V, X, complete Fields of Ruin and the battle of Fort Trinity (Personal Story) or buy them for 60 silver and 7 skill points
3 – VI, kill the champ krait witch in Timberline Falls or buy it for 10 silver and 2 skill points
3 – III, complete Retribution (Personal Story on Claw Island) or buy it for 10 silver and 2 skill points