If its set to 3 turns, I dont see how it will be any more powerful than a phase shield. In fact, it will have disadvantages that a phase shield doesnt have. I would almost say at 3 turns, phase shield is better. Sure momentum can get through phase shield, but phase shield doesnt leave you with 1 hp. Perhaps thats why Zanz has it set for 5? The stalling potential at 5 turns is what worries me though.
List of counters for the elements for SoS:
-none
-none
-steal, liquid shadow
-none
-pulvy
-antimatter, purple nymph
-explosion
-none
-none
-holy flash
-sundial
-none
Also user can not use any healing cards.
Compare to phase shields weaknesses
-none
-none
-steal
-poison
-pulvy
-none
-explosion, fire bolt
-momentum, chargers
-none
-none
-none
-ice bolt
it was a quick list, so I probably missed something on both sections though...
edit
If you want to get technical, I could add cards such as lightning or shockwave to both catagories, as you could attack your own creatures when SoS is on the field, or target the opponent directly if they are using Phase shield, however, I am trying to keep the list to things that are either continuous (like using liquid shadow to make an opponents creature hurt instead of heal) or could be deadly (holy flash can easily be deadly against SoS, and Fire/Ice bolt have huge damage potential against phase shield, meanwhile unless the opponent is hurting when the phase shield is played, lightning would just cause a small dent in HP)