If you're looking for a decent assault rifle, try the Karak. It's main drawback is a 30 round mag. On the plus side, it has a polarity matching Serration. My Serration is at +75% damage, I think, and with elemental mods to suit the enemy type it'll handle T1 Void with no problem. Was also using it against lvl 20 Corpus and it was holding its own.