La habilidad seria esta, al lanzar la habilidad al enemigo cause x3 de daño de la fuerza del heroe.

[gui]
Event
   Unit - A unit begins casting a ability
Conditions
    (Ability being cast) equal to Storm Bolt
Actions
    If (all condition are true) then (do actions) else do (else actions)
          If - Conditions
               (Level of Storm Bolt for (triggering unit)) Equal to 1
          Then - Actions
                Unit - Cause (triggering unit) to damage (targeted unit),
                dealing (3.00 x(real((Strength of (triggering unit)(include bonus)))))[/gui]

Usa el evento Starts Effect y saca ese If de ahí que hace que sólo dañe si la habilidad es nivel 1. Y tienes que usar Target Unit of Ability being cast

Sigue sin hacer daño y el If esta ahi por necesidad

EDITO:

Ya esta, gracias

[gui]
Event
   Unit - A unit Starts the effect of an ability
Conditions
    (Ability being cast) equal to Storm Bolt
Actions
    If (all condition are true) then (do actions) else do (else actions)
          If - Conditions
               (Level of Storm Bolt for (triggering unit)) Equal to 1
          Then - Actions
                Unit - Cause (triggering unit) to damage (target unit of ability being cast), dealing (1.00 x(real((Strength of (triggering unit)(include bonus)))))
    If (all condition are true) then (do actions) else do (else actions)
          If - Conditions
               (Level of Storm Bolt for (triggering unit)) Equal to 2
          Then - Actions
                Unit - Cause (triggering unit) to damage (target unit of ability being cast), dealing (2.00 x(real((Strength of (triggering unit)(include bonus)))))
    If (all condition are true) then (do actions) else do (else actions)
          If - Conditions
               (Level of Storm Bolt for (triggering unit)) Equal to 3
          Then - Actions
                Unit - Cause (triggering unit) to damage (target unit of ability being cast), dealing (3.00 x(real((Strength of (triggering unit)(include bonus)))))[/gui]

Te doy un pequeño tip. Viste que el lvl 1 hace 1xfuerza, el lvl 2 hace 2xfuerza y el 3 hace 3xfuerza??
Ves qué hay un patrón? Ves otra solución aparte del If?

Usar variables talvez? no soy muy bueno con esas cosas