Planetfall spells are tricky to use properly and it is very good. Even higher tier spells don't do much if used at wrong time. Consider mass insanity. It will give you like 20-60% chance to apply berserk, not a big deal. But see what happens if you use it properly. First you use hero ability to reduce psi resistance by 2 on all units, it always works. Then you shoot with some psi units (malictors are optimal) which have ability or mod to reduce psi resistance again at the units which have the highest potential (but don't kill them!). Finally you cast the insanity spell and try to kill dangerous units which resisted the spell. It results in massacre next opponent turn.