got a heph with curse and blessed aim, wonder if its a good alternativ for fana

Echoing strike doesn't use attack rating, so that aura is useless for warlock.

so it should at least be cursed and fana right?

Always cursed. The main mission of your demon is to cast amplify damage. For that, the best auras are cold, fire and light. Because they apply amplify when the aura ticks, not only when the demon attacks.
Cold slows your enemies but doesn't work with bosses.
Fire and light both work in bosses and have a bit better area. The differences between these two are small. So use the one you find first.

Only thing that matters if they’re cursed.