Actually, psionic isn't that bad in SS2. The marine is the worst I find.
For psionic, healing and attacks are all you'll want. All those little 'could be nice' are pretty useless in the end.
Here's a little something that might help you. If I'm not talking about a weapon, it's because it sucks and you don't need to raise that type any higher. You can always raise them more for the extra damage (like heavy to 2 is really cheap).
- 3 for shotguns
- 6 for assault rifle
- 1 for Energy pistol
- 4 for rapier (not really good, but still better than the wrench)
- 6 for EMP rifle
- 1 for grenade launcher
- 1 for crystal shard (research 4 too)
Since ammo isn't too common, you'll want to keep a melee weapon. The wrench is that weapon for a long time. If you go for energy you can upgrade with the rapier early enough, but if not, you'll have to make due until you get the crystal shard.
I highly recommend the crystal shard and even raising exotic to 3 for the bonus damage (3 is still pretty cheap too). It is by far one of the best weapon in the game and it saves you ammo.