I play a Sage and my survivability has been greatly reduced without the instant lift, even with force barrier.
I don't know about shadows but if phase walk really upped their survivability why not add an extra reduction in the lower tiers of sages/sorc specific trees; I was thinking of adding a 1/3 second reduction in Chain Shock/Upheaval per point and increase the time reduction per point in Haunted Dreams/Containment to .5 per point. Now, I agree this might benefit Full Lighting/Telekinetics survibability more than you want to, so maybe you should take out the Whirlwind/lift reduction from Suppression/Blockout maxing the reduction for them and maybe healers to 1 second, which in my opinion it is not a big upgrade and I doubt a lot of healers will take it for 3 points.
Once again, this idea is only if shadows really have a good time with heir current survivability.