When would I use Arcane Strike instead of Disintegration Wave?

Solution 1:

Arcane strike's big winner is it also acts as a knockback. You can chain knockback non-elite enemies to death, effectively trivializing large packs of dangerous monsters which your disintegration wave may not kill off immediately.

Basically, a safety in case something dangerous gets too close.

Solution 2:

Arcane Strike is better than Disintegration Wave when you have a large number of enemies in a cone or semicircle shape in front of you, instead of coming at you in single file. In those cases Arcane Strike will hit all of those enemies, whereas Disintegration Wave only hits those in a direct line with it.