So currently Surecast prevents a cast from being cancelled by mobs who deal enough damage to stutter it.
What could be done? I think either of these could make this skill more worth it to pop.
Casting a skill would continue to go off, so long as the target remains targetable, even while stunned as long as the cast began before the stun.
The next spell losses it's degree of casting limitation and can continue to cast even as the mob moves behind the player. This would not increase range.