ah by the way, The ability (AgilityStrike), leave it an evasion ability with 0% evasion, and 3 levels, so you can learn it, but it does nothing, the triggers do its work,change its icon and name and whatsoever tooltips and description
i expect you to do it yourself, to learn some intresting things in triggers.
anyway, if you want it to look like critical strikes (with red values) , try using the Floating text action,with font colour 255,0,0 and if you want animation and sound for it, use the play unit animation action, and use the Play- 3D <Sound> on unit action in triggers, have fun.