I don't think that's a trade that would work for either squad.
Toronto is looking for an immediate solution to their goaltending woes. I don't believe the 2-3 years left to develop Visentin would be that appealing. I think Burke would look at a Bernier long before he set his sites on Visentin.
From Phoenix's perspective. Visentin is a former ohl goalie of the year and arguably should have repeated this year. He's Phoenix's goalie of the future and is projected to make the squad as a backup within 2-3 years. Phoenix will be patient.
Kadri is intriguing from Phoenix's end. There might be some interest from Maloney to reunite Boedker with his former linemate. That being said I'll nix the Gormely discussion right now. No chance Phoenix makes that move.
Goalies are a different breed and take twice as long to develop as a position player. Also, you really never know what you will get out of a goaltender. The Leafs are better to hold on to Kadri and hope that Sparks continues his development.
As for Phoenix, I think that Domingue will be a better NHL goaltender than Visentin. Visentin has had the advantage of having a very solid team playing in front of him for the past couple years.