Lol you think that would be “enh level”? Try 1.5m CD, all damage reduced by 20%, feint nerfed to 5%, vanish reduces your damage taken by 40% for 5 seconds after appearing, evasion 30% dodge chance, Shadowstep CD tripled.
If you read Shimmer properly it doesn’t disrupt casting of any spell school. It being limited to Arcane only spell school would disallow to Shimmer during Greater Pyro cast for example.
That is NOT THE CASE already.