Even though it might not be futile, hate and vengeance are powerful motivators to develop such attacks. If Diagram magi cannot brute-force Cultivators, the next best thing is to use esoteric attacks to kill them. Even if its unfinished, we may find their notes useful, as we found Baelixnaire's notes on Quickening useful.
We know, and they know, that esoteric attacks are pointless against decent level Cultivators as they can't hit them in the first place. That's why it's a waste of effort and a spell slot to develop them when you could instead keep it for something that would actually be useful.
These are magical terrorists. Their game is killing off cities of mortals and scrub tier Cultivators, people they don't need esoteric attacks to kill, just large scale area effect attacks.
Basically, there's no one for the Diagram Magi to target with these effects
This is the point I can't find myself agreeing with. We did indeed puck the low-hanging fruit of what Baelixnaire knows, but he's only one man with limited specialties, and we're clueless on what other synergies there may be with powerful spells in other categories that Baelixnaire did not know. Remember the Liches were out of contact for thousands of years, and they spent much of that researching without communicating that research.
Why would a Death spell help with Cultivation speed for example? What's the reason to believe that there's some unlooked for synergy amongst the other Signs? Chronomancy is obviously beneficial, as is Transformation and Divination.
Because they were at some point a strong martial culture who destroyed all other paradigms of magic, killed the Orcs, etc.
Spells developed in those times should be available to people a thousand years old.
They don't know it scales with Cultivation, since they cannot Cultivate. However, we may find out how to scale esoteric attacks like we did for Alvan's Crown using Ego Barrier.
Grandpa Yong is over five thousand years old. Baelixnaire was over seven hundred years younger. They defeated the other external magical disciplines thanks to their mastery of dispelling. Given they could break their enemies' defences that way, and then kill them with conventional blaster magic, why would they need to develop esoteric attack forms?
We're also talking about enemies defeated before the Diagram was Ascendant, several thousand years before the Cultivators arose. Is there any reason to believe that there are any liches surviving from those pre-ascendancy days? The Diagram were a strong martial culture once, but they became lazy and complacent, which is why the Cultivators could develop for hundreds of years unmolested.
Yeah, Alvan was merely the Fifth Scourge of the Diagram Realms! At least four other Scourges should have possessed unique spells.
And those spells would survive because... We're dealing with the remnant of a remnant of a remnant of a world spanning Empire. Nearly everything that they were is lost to the sands of time.
You're essentially going all in on an option that we have literally no idea what the distribution of pay offs are. I'm at best hoping to get a Beyond Vault out of this.
Besides, we can upgrade virtually any Diagram with Artifact.
Only if we Cultivate, which the thread is generally unwilling to do, and spend large amounts of time to create the artifact. We generally don't have time for artifact creation on spells that don't pay back more time than was invested in Cultivation and Artificing to make them.
