Just because he has no direct damage abilities doesn't mean he's bad, in fact;

Decoy = This should be self explanatory, in a big group of enemies you place the decoy and distract the enemies so you can get away or to help during defence.

Invisibility = Great in general as if you're getting swarmed by any faction you can become invisible and get away to use your weapons.

Switch teleport = You can use this plus decoy to get to difficult to reach places, very useful.

Radial disarm = Beyond useful for corpus and grineer as it stops the barrage of bullets flying at your face, also super useful for void as gunners and fusion moa's suck.


Now, unless you're incredibly bad at the game and don't know how to play strategically, loki is very useful in nearly every scenario.

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Although it's based on play style, some people can't handle frames outside of frames with an immortality button of cheatycheat or things of that nature. -coughrhinocough-