Leaving the "should" and "should nots" of AI empires aside, here's the reality of the situation: AI will generally not approach threats directly if it doesn't feel like it's capable of actually handling the problem head-on. They generally don't consider the greater picture and will stand by, attempt to attack easy targets, and hope for the situation to change - which I would say is generally a pretty safe approach for an AI that simply can't be expected to approach such a situation with the delicacy that a player might be able to.

But it's also very annoying when you rely on the AI to combine their strength, which is why there's a general rule in Stellaris, that whatever Empire you decide to play, its end goal should always be to accumulate power yourself so you can actually face and solve a problem yourself. Yes, that stays true for subject-based playstyles, and for diplomatic empires as well, the power should always center around you in the end.

If you're not doing that, then whether you like it or not, you're implicitly signing up for having a bad time the moment some actual threat appears on the galactic stage. If you want to continue playing like that, you should either reduce crisis strength significantly so empires feel like they have more of a chance of actually fighting, and to make sure you can defend yourself regardless of what other empires happen to be doing. Or, move back the endgame date to give everybody more time to grow stronger.

It's a hit or miss, I have had games where an AI empire actually comes in with a surprise 200k fleet and solos the damn thing (Not even Fallen or Advanced)

Most of the time AI kinda get stuck in a loop of stagnating subjugation, forever wars and whatnot.

The most successful ones manage to form a Federation from what I've seen.

Yeah, the AI is typically pretty useless at these things. The snowballing aspect of fleet combat creates a lot of problems here because a lot of the time, the AI could throw their entire navy at it and do nothing. It's too easy for fleets to just get deleted without doing any damage.

Originally posted by Ryika:

They generally don't consider the greater picture and will stand by, attempt to attack easy targets, and hope for the situation to change - which I would say is generally a pretty safe approach for an AI that simply can't be expected to approach such a situation with the delicacy that a player might be able to.

Wow, this is just like every government ever. How did they get such realistic AI?

I once had a game where the crisis appeared on the other side of the galaxy to me, so I started turteling, ready for a fight...only to look again when nothing had happened for a while and found that the Crisis had been absolutely smashed by one of the AIs.

Vassals thinking that their overlord would actually risk its neck to protect them is really sad and hilarious at the same time.

I once saw an endgame crisis spawn in the middle of the biggest battle of galactic history, the final battle of a War in Heaven with everything both Awakened Empires and all their allies could throw into the fight.

The Unbidden couldn't even get out their opening transmission before every last one of them along with their portal were vaporised by every form of weapons fire imaginable, and the endgame crisis ended approximately 1.5 seconds after it began.

Originally posted by ImperiusDamian:

The Unbidden couldn't even get out their opening transmission before every last one of them along with their portal were vaporised by every form of weapons fire imaginable, and the endgame crisis ended approximately 1.5 seconds after it began.

The Unbidden: "...feeding ground reached... prey bounti-"
"The last vestiges of the extradimensional invaders have been wiped out!"
Everyone in the Galaxy: "Huh?"

Originally posted by Comrade Burrito:

Originally posted by ImperiusDamian:

The Unbidden couldn't even get out their opening transmission before every last one of them along with their portal were vaporised by every form of weapons fire imaginable, and the endgame crisis ended approximately 1.5 seconds after it began.

The Unbidden: "...feeding ground reached... prey bounti-"
"The last vestiges of the extradimensional invaders have been wiped out!"
Everyone in the Galaxy: "Huh?"

Everyone in the Galaxy: Must have been some weird space weather. Let's finish murdering each other to see who was right, the Vorlons or the Shadows.

By the way, Extradimensional Invaders are supposed to be particularly attracted to Psyonic species, especially if they've made a pact or have a Chosen One. Could explain why they beelined straight for you.

If you're the head of a federation or the custodian(not sure about this one) you can lead the combined fleet of your federation against the enemy if you activate the "take point" function of your fleet.

Or at least it did the last time I used it. Was pretty epic to see the entire galaxy attacking the threat as one.

From what I've observed the AI takes a bit to actually start fighting a crisis once it starts. At first this happens because the AI usually doesn't consider the crisis to be a threat (mainly when the crisis is NOT close to them), but even if it is close it still takes time for them to react. You know, just like IRL red tape bogs things down for stupid reasons.

Once the crisis actually starts going though I've noticed the AI has a tendency to pile on it and utterly curbstomp it back into the void. Especially if fallen empires still exist (i turned the off because of this, they trivialize crisis situations).

I've also observed crisis actively spawnkilling each other a few times (unbidden showed up right in them middle of Prethoryn territory, then got REKT as soon as they engaged).

Originally posted by ImperiusDamian:

Everyone in the Galaxy: Must have been some weird space weather. Let's finish murdering each other to see who was right, the Vorlons or the Shadows.

I think both races are obnoxious and morally questionable, the question is whether either side would be happy to be proved right. Don't put your hand in a wasp's nest and you won't get stung.

In my first game of Stellaris, The Unbidden spawned on the opposite side of my galaxy and for some reason made a beeline straight for a Fallen Empire.

Unfortunately for The Unbidden, the Fallen Empire were considerably stronger and pushed them singlehandedly. I recall the galactic community hailing the Fallen Empire as the saviours or something similar!

Originally posted by Static-ghost:

Originally posted by ImperiusDamian:

Everyone in the Galaxy: Must have been some weird space weather. Let's finish murdering each other to see who was right, the Vorlons or the Shadows.

I think both races are obnoxious and morally questionable, the question is whether either side would be happy to be proved right. Don't put your hand in a wasp's nest and you won't get stung.

A lesson Londo Mollari learned rather too late.