My theory on Loki...

His kit IS good. How is decoy ridiculously strong? I just think there needs a small buff to decoy to make it more effective vs gods and / or have vanish cooldown reset upon death.

Early lane phase being able to harass without taking minion aggro. It also does a lot of damage IF you can manage to hit a enenmy god with it, which really ain't that hard when you got your ultimate.

Yeah but unless you're leveling up decoy first then the rest of your damage is poop. And if you level up 3 and 1 first then decoy isn't really good damage.

It's good damage at level 1, but by level 3, unless you've been putting points in it, it will practically be a distraction-only skill till lvl 17-8 when you can notice the damage.

IMO Loki just needs a little nudge. I frankly think his damage output is already pretty good and he doesn't need anything too crazy.

I think that making Loki a bit harder to just focus down is a better way to go to make him a tad more viable.
I quite like some of the previously mentioned suggestions.

First of all I think Decoy needs more use. Early-mid game it's a decent way to distract the minions; but frankly it doesn't do enough vs enemy gods and especially in mid-late game when minions are just a minor nuisance this ability. It's a pretty great way to clear waves when you get it to a higher rank, but it is hardly ever worth sacrificing your burst abilities for (unless you solo a lane or something).

A slow or maybe even a mesmerize effect (on use, not on pop) would be nice. I also like the idea of it "absorbing" enemy attacks like earlier mentioned. It doesn't need health or make you lose control as someone suggested before. It would simply divert and absorb attacks that would have hit Loki (or maybe just those that go through the decoy AoE field).
This would make Loki a bit less easy to just burst down when you try to gank someone. Especially late game when the other team is a bit perceptive it can be easy to just obliterate Loki as he jumps in for a kill.

A cooldown reduction on vanish would also be a way to go at things, as long as it has a certain condition.

Putting more stuff on his ultimate might not be the best though, seeing as Loki is already extremely reliant on it (as in his whole way of killing people pretty much revolves around it) putting more pressure on that might be bad.