My question is when you use the multiclass feat Sneak of Shadows for the 1/encounter sneak attack damage, does it increase by tier like the rogue class feature Sneak Attack, Heroic: 2d6, Paragon: 3d6; Epic: 5d6. I would assume it does.
Sneak of Shadows increases as your level does. Taking a multiclass feat gives you the full rights and privileges of whatever you qualify for in regards to the additional class.
In this case Sneak of Shadows grants you the ability to use Sneak Attack 1/encounter as a rogue of your level.