I'm a bit pushed for time at the moment, and was planning on reading the whole of the OP/thread before responding, but I've just got to quickly comment so I apologise if it's already been addressed. I'll read the rest later and get back to it.
Steal "beats" phase shield, because in addition to gaining 2 quanta, you also gain the remaining turns of the phase shield.
This is not necessarily true. If you have no shield, then stealing Phase Shield will be a net gain for you. If you have a Bone Wall with 83 layers, then it will be a net loss. If your opponent has creatures which are Immortal, then Skull Shield or Spine Carapace may be more useful as the only way to kill those creatures. If your opponent is playing a hand using Psions and/or Shards of Wisdom, then a Jade Shield or Solar Shield may be of more use than a Phase Shield. If your opponent has Pulveriser or Explosions or other Permanent Control, then a shield that is Protected may be of more value than a Phase Shield.
Steal is a more complicated card than you're making it out to be and using it, even to Steal a Phase Shield, may have a negative effect on you.