Don’t forget that confusion depends on Condition damage to scale.
with enouth in illusions (15pt) you can have faster illusion cast, longer confusion and shatter stacking confusion.
F2 with 3 illusion can stack 6 confusion, synch with Scepter 3 you can add 11 stacks or another 5 after the firsts 6. and giving 1000+ damage with 800-1000 in condition damage.
You can alternate F1 and F2 almost all the time with 3 illusion. and more with illusion XI (Illusionary personna) adding 1 stack.
I used to use that, with Inspiration V and the signet of illusion life (20%+50% illusions life), adding retaliation to fantasmes, with 15 you can give regen to illusions, and shatter them for confusion.
With prestige bubbles or Staff 5 you can make your teamates to trigger confusion or mass confusion on ennemis. Adding more confusions stacks.
IMO it’s easyer for mesmer to stack confusion and retaliation, than fire, bleeding or any poisons conditions.