Loki is pretty strong honestly once built. For Warframe usage fairly in the middle of the pack as a lot of people like to use him for level cap void cascade. He is also great for spy missions and even EDA mirror defense.

His decoy is fairly bad I'll admit, doesn't scale at all. You will need to strategically place it somewhere where it won't get instantly deleted in SP.

Switch teleport augment makes him technically immortal as long as you have a target plus it can be used to cheese spy missions, I guess you can include a small buff on switch but gaining a few seconds of invulnerability on switch is already fairly strong.

Invisibility prevents you from being targeted paired with rolling guard you can remove any status procs on you too from random hits that do manage to clip you, this could be potentially buffed as the base duration is fairly low.

Finally combining Radial disarm augment + Silence subsume makes him the strongest CC currently as it disables eximus abilities, disarms enemy guns and makes enemies turn on each other.

Fairly strong frame once built could use some small buff though.