I'm having a hard time reaching gold in the Psionic Assault challenge in Starcraft 2. I managed to get silver using combinations of force fields and psionic storms, but it seems that leaves me with too little energy left for the last waves. I usually end up being gg'ed right after hitting the silver mark.
I tried morphing one or two Archons after some of my templars exhausted their energy, but that only helped surviving for maybe a couple of waves. What's worse, the waves come too fast for the archons to regenerate their shields, and they're no longer capable of storming after that so I guess this is really only useful for making a last stand.
I feel I must be under-using the sentries, but every attempt I've made at using hallucinations or guardian shields only seemed to eat their energy faster without helping that much in destroying the aggressors. And without shielding they die just too fast if I send them in battle.
Am I missing something, or is it just a matter of getting a better mileage out of force fields and storms ?