-Warp's passive shields are based on current health, not total, so it isn't too effective at saving a dying ally
-Warp has very low HP and Regen, so even with her shield she is very easy to kill.
-She does however have slightly higher mana regen than most, allowing her to stick around a little longer.
-To compensate for her low HP, the Zealots are extremely tanky and scale extremely well. Using them as her front line, rather than Warp herself, helps keep her alive.
-If that isn't enough, Warp can place her Warp Prism near the fight and Hearthstone to regenerate HP and Mana, allowing her to quickly return to the fight with full stats.
-Overall her abilities work extremely well for sustained fighting in one area, such as Cursed Hollow Tributes or Blackheart's Bay Turn in point.
A cloaking field around it as a passive would be, in my honest opinion, too powerful. If it has a cooldown a bit lower than tyrande's ultimate (the cloaking one) and has to keep around the core, then I think its power would be.. alike to Time Warp's, which I think as a tiny bit too long of a cd.
Yeah, I guess the effect is kinda weak for a 90 sec coodlown. I dropped it to 60.