Nirth: When it comes to psi skills, are they primarily defense or utilitiy based? Or are their offensive abilities that means you need less focus on weapons.
There are some from each category actually. There are those that increases stats, there are those that deal direct damage, those that messes with the enemies, those that helps you find things, and those that helps with different tasks.
Do note that with the great versatility of psi powers comes a great cost, so it is balanced.
And don't skimp on the maintenance skill, it is highly useful. Do skimp on Heavy & Exotic weapons though, those are basically beginners traps.