Honestly MammonAzrael, from Peach's response and the first part of your response, I was alreading thinking of scrapping this, but if you believe this can be salvaged, then I'll try my best.

Anyway, I nerfed the class. I don't think this is enough by any means, but I nerfed it, and we'll go from what we've got.

First off, yeah, I've been misusing 'cheesy'. I thought it was the same as broken. Stupid of me.

Anyway, I changed deadly skill. It's only your dex modifier now. Also, 'Archer not a Fighter' got changed a bit. You count your BAB as average for multiclassing; as if you BAB was the middle ground between awesome ragned attacks and horrible melee.

As for rapid shooting, the reason why I didn't choose rapid shot was because I specifically wanted the True Archer to be better than a fighter who just took rapid shot as a feat. I changed it instead to basically rapid shot for all attacks.

Sniping means if you hit with your attack after studying your opponent, you automatically critical. You have to hit first, as in roll to hit. As for confirming critical, if it's too much for an automatic crit, then yeah. You tell me if it's not. For the concentration checks, think of the True Archer as a wizard, so choose concentration DCs that way, only you don't add the spell level of the spell being cast, cause there's no spell, and you're just basically studying your opponents movements so you can predict where he'll move when you aim for his eye.

I changed improved range according to your suggestion, though I'm keeping overdraw 1 to 1 for now.

Multishot: You do know that multishot is basically just manyshot and improved manyshot together, right? Improved Manyshot takes off a limit to how many arrows you can fire. Admittedly, it's in epic level, but still, it's the same thing.
Anyway, I changed Eagle Eye so that's it's just a bonus to hit, so no bonus attacks. Does this mean I can changed Multishot to a no limit one? With the nerf, it basically is manyshot and turns into improved manyshot the moment you turn level 21, which coincidentally the same time you can get that feat.

For hidden shooter, I changed the bonuses. As for precision, what I put in right now was wrong, disregard that. I just put it in to have something there.
I liked your suggestion that it's basically just a bonus to hit for when you're taking penalties, but the problem is that there's already stuff like that. Improved Precise Shot already negates all concealment and cover penalties.
Unless...do you take penalties when you're entangled? Or like a spell that physically weakens you? If you do, precision could perhaps be an ability that negates those penalties, like focus under duress. But I don't know how to word that if there is. I'll need help.

Improved Hidden Shooter: Yeah, for some reason I missed what you said.Your suggestions are all good. Question is, just one of them, or both?

Deadly Precision: Uh-oh. You gain sniping bonuses for ALL attacks in the next turn. Overpowered then, huh? tell me how much even with the nerf.

Elemental Shot: It came from the original class from the D&D wiki. I thought it would be a way to cause more damage than normal, reserved for boss encounter, or for when the Sniper meets an enemy immune to critical. I weakened it. Tell me what you think. Also, it neutralizes poison because the arrow turns into its element. I don't think a poison would remain viable if it's on fire, or in contact with acid, or supernaturally cold, or not sticking to the arrow because it's lightning. Poison stays with golden arrow because it just turns into (magical) gold.
Golden Arrow: No, you do not critical with this. Ever. Unless you're a sniper, then you auto-hit and crit.
For both augments, I'd rather it stay at higher levels. As for what mental stat, what should I use? Intelligence? Wisdom? Or charisma? I'd rather it stay this way, but if you really think so...

I switched the names for greater and advanced.

Rain of Arrows: I nerfed it. No more rapid multishot of golden elemental arrows. Just four shots of golden elemental arrows at the max. Honestly, I want to keep the DC the same, so that it scales at higher levels. Tell me what you think.

Killing Shot: It's a minus to hit. I'm keeping the forced crit, but I dropped the coup de grace. And with the new eagle eyes, you can only get up to four attacks at level 20, disregarding magical weapons and stuff. So no, no ridiculous number of attacks.

A note about sniping though, since its lethality is from specific aiming, should I make it so that when splitting or multiplication of arrows you only critical with one arrow? Because unless the multiplied arrows all hit one spot, it doesn't make any sense for all of them to critical.

Instinctual Lethality: If you think it's not good enough, well, I don't really know what else to give the Volley Archer, since most of the problems seem to come from it.

Slaying Shot: Changed it to slayer. Also, perhaps it should instead be like

When sniping, you double the critical increase, so x2 to x3, x3 to x5, x4 to x7. And I should probably change it to just bows.

So, tell me what you think.