The problem with plasma is that it is overkill for most enemies past the early game. Its a boss killer, whereas the laser pistol is your main workhorse and the electropistol is idea for certain situations. Most epistol players use a laser in one hand, electro in the other, and carry a plasma for bosses and the like. If you were going to main a plasma pistol, I would go for maxed/near-maxed dex with versatility, 6 or 7 per, 10 int, and 4 or 5 agi. They already do gobs of damage, so you would aim for more shots.