Some players think that diplomacy still needs some work. There are some issues, like AI not respecting non-agression treaties, or razing cities in one turn.

Anyway, I think that currently, AI can't try Spell of Making or Master Quest to win, so they are oriented towards conquest or alliances.

Two tips:

- The AI seems not to attack untill they have expanded enough

- AI seems to rely on Faction Power to determine if it is moment to attack, once it has expanded

When my Faction Power is above AIs, they offer me treaties, alliances,... but when is below, I'm dogpiled like you said.

So try to expand and build a strong army to keep your Faction Power high. Leveling champs will help too. Then, AIs will attack theirselves, instead of you. But if any of them tries to attack you, send your army and make them repent.

I'm with the OP. Diplomacy, at this point, is messed up beyond belief. 

There are very important 'weights' missing (fighting-my-enemy, headed-to-a-win, i-am-losing-a-war-already, my-ally-for-a-allied-win)

There are also 'weights' that are too light. (aggressor-of-opposite-alignment, i-am-peaceful, still-expanding, too-far-to-bother, )

And finally, there's some behind the scene mechanism that is connected to power difference, that seems broken to me.

What Stardock should do is tie their diplomacy guy to a chair, and make him play ten games in a row on expert on a large map, so that he sees what strange behavior AIs exhibit.

Yup, I agree, It's odd.
I've also put some observations on diplomacy in my opinions/suggestions thread: https://forums.elementalgame.com/436220

With the OP, as well.  It isn't that the diplomacy AI is bad, as much as that it lacks nuance through additional options, has a few glaring faults in its conditionals, and lacks flavor.  None of this is the sort of thing that resists all efforts to fix, and all of it has been done well by Stardock in the past.  I just figure they wanted to get the game released in time for the holiday rush, and diplomacy was viewed as sufficient to get out the door in its current state.

Hopefully, it won't stay this way for long.  They haven't made much mention of it, but surely they can see it looks poorly next to GC2.

They don't just look at your "score" they look at your army ratings. The problem is, the game has a terrible army strength rating system (you see this in the weak-medium-strong-epic badges), so it's not very consistent. A well design medium strength army could wipe the floor with a strong one, so they declare war thinking they are stronger only to get their clocks cleaned.

The rating system needs work, the diplomacy system needs work... along with some more intelligent AI behaviours (teaming up to fight a strong foe).

Right now, the only way to keep diplomacy in play is to be much stronger than your opponent. Big stick diplomacy.

Except it ignores over half of these. Wouldn't you call that broken? I've had perfect relations with a faction, all +'s except for a few -1's and they join the band wagon of attacking me when they were AT WAR with who I was fighting.... Doesn't that seem ridiculously outrageous to you?

I honestly have made up my mind, I refuse to ever recommend this game to anyone until they fix the AI...

Last Game: I was doing fine, Made a few Alliances with my Faction, had 3 "friends" past the 75% mark of liking me. I also had 4 Empire nations liking me as well, which was hard. But I did it.

Ythril attacks me, I take out his city in a matter of 2 turns. But now I'm spread out, its still early in the game, and I only have 2 Armies, which are spread thin. Guess what happens? 1 Empire faction after another declares war on me, 1 after another. Now I'm getitng hit from 6 different sides, including the 4 Empire Factions who liked me... ALot... jump on the band wagon of hitting me.

All right, so I'm sitting here thinking, wtf are my friends doing? Some of them have war declarations but refuse to attack, since its early in the game I know the enemy has all of their army's in my land, so why are my friendlies not doing anything to hit their cities?.... FAIL. Fail AI

So I'm stuck fighting the entire Empire while everyone else is twiddling their thumbs, and refusing to join the fight.

Which I've noticed the AI does....

The AI will attack you 1 by 1, constantly, every game making it a 5v1 or more, but what do you never see? You got it, your Allies, Friends, etc. doing the same for your enemies..... Why is that?

Diplomacy AI has a serious flaw, MAJOR flaw. The AI for deciding who to attack, when to attack, and who to help defend has a massive flaw as well.

These are CRITICAL for a good 4x game, CRITICAL. Without it, its like building a house out of sand on the beach. Its not gonna last long when that storm hits, and you'll find everything is broken and unworkable because your foundation no longer exists.

I'm putting this game on the back shelf until these issues are resolved. I've finally made up my mind.