I dislike hard-counters and much prefer soft-counters. Hard-counters tend to quickly devolve into situations where either you can predict who wins from the get-go as you already know your chances of winning are neglicible or results in situations where it's just a matter of whoever's first with their mechanic(e.g. assasinate before I summon you win, summon before you assinate I win). I prefer soft counters, which in this case would require spreading out the power of the mechanic a bit from the slann.
Yeah but they won't do that. I imagine they already discovered how dumb conjuration can get with multiple Slann during playtesting, hence the General requirement (as in Matched Play you can't choose a new one mid-battle). Same reason why Astrolith is the only other thing that generates Conjuration, it's an expensive and easily killed utility hero. It's not a 'soft counter' to have greater redundancy lol. Slann are already quite a tall order to assassinate. If they're no longer the loci, you'll just see hero spamming lists.
Furthermore there's a bunch of "problems" with the mechanic regardlles. It al depends on 1 model, making it basicly mandatory due to its power. The mechanic works by going against what that model should be doing and makes it just sit in a corner looking pretty. And it doesn't scale in any way shape or form with the size of the game. All of these could be mitigated to some degree by moving some of the power towards other models. Have skink priests increase the point generation, have a slann still able to cast if he's next to an EoTG, have an endless spells that interacts with it, etc. Plenty of options that leave the slann as the crux of the mechanic but that remove the current problems.
I disagree. Slann were never damage dealers prior to Conjuration, you never moved them around much anyway because they need to be screened and protected, and the old summoning was much weaker as a mechanic (and limited by their spell casting per turn, and subject to unbinds/failed casting rolls on top of that). In a way, Conjuration has toned down our teleport ability, because now you need it to move both the Slann and Astrolith.
It is already scaled by how expensive the combo is, at 1k you can probably only afford the Slann+Astrolith realistically, and at 2k it's still over a quarter of your list gone on utility, not damage output. Shunting Conjuration to other models would mean Slann would get dropped out in favour of hero spamming. Engines already interact with Slann just fine, making them even more auto-take isn't a good way to go IMO. Balewind+Cogs already supercharge Conjuration in ways no other Endless spell does, and I doubt our faction-specific ones will be as powerful (unless GW want to see us bust out a Dread Saurian for free Turn 2).
You're also kinda ignoring the thematic aspect to the ability. Slann are the only means by which Seraphon forces deploy (even if they're not on the battlefield physically). It doesn't make much sense for the memory-clones to also be able to conjure up reinforcements.
I don't want the mechanic "enhanced" I want quality of life improvements given to it. I'd gladly take a nerf to the mechanic if there were ways to support it using other models due to the sheer increase in quality of life.
But you are asking for enhancements, by introducing unnecessary redundancy and power. The current Conjuration is completely balanced by the fact that when the Slann dies, the whole strategy dies with him. It will take an Astrolith rolling max points for 2 turns straight to bring down even the cheapest reinforcements. Depending on how many points you're proposing each Priest can generate, it may be that the Astrolith gets shoved out the door as well.
I think the damage soaking component of his suggestion might be a tad much. But I'd love for projections which we could use to cast through and switch places with. It'd be a neat mechanic. Especially the casting/summoning through it as it can help circumvent some of the position restriction.
Spellportal already does that though (it has been nerfed into the ground admittedly, but that's its function, arcing spells). We also already have unrestricted teleport, potentially twice, which can't be stopped by any means, so positioning your Slann is pretty easy tbh (and if we're talking Conjuration, you only need to move the Astrolith where you want reinforcements to show up).
I think an Endless spell for new conjuration/summoning loci would be the least offensive option, as the enemy can always just unbind/dispel it, it can't move, and it only matters if Conjuration/summons is still a threat (not to mention that the Seraphon player has to waste a spell casting the Endless loci in the first place). Maybe some kind of Totem? I'm still annoyed Stormcast already stole the comet idea for a faction-specific, it's not like they need extra ways to generate MW bubbles.