Hello, I guess this is the best place to post this on the forum, even though it is not a scenario per se. I started playing WH in 7th edition, and saw many problems with how the magic phase evolved into 8th.
For several years I thought about how to amend this, and last year, having learned a bit more about
game design I started writing my own custom rules complete with 8 base lores and some army specific lores.
(I haven't experienced all the WH armies in action, so some are missing.)
I will link to a live google doc below. It is largely finished, but I am still working on balance and clarity from time to time.
The document includes a preface to explain what I wanted to change about the rules, general rules about the magic phase,
and a table of contents with clickable shortcuts to each of the lores. In my own opinion, each lore feels like it has an identity, and the few times we have tested it (about 10 or so games of varying sizes), the magic phase has been really interesting, yet not too powerful.
I would be very happy if someone here were to read it or even try it out and tell me how it went. Any response is welcome.
The biggest problem I have with your system is that it completely cripples an Army that chooses to play without Wizards, in their attempt to defend against spells. In normal 8E, a wizardless Army could have 6 dispel dice, which they could use to stop almost definitely one spell, and sometimes two. Your system gives a wizardless Army a maximum of 3 dispel dice.
The second issue is that you are doubling down on the benefits of being on the offensive side, by not only having the offense more likely to have more power dice, but also giving them full value for their wizard level when they cast, and giving the defense a bonus based on wizards in proximity to the target, which could possibly be no bonus. Now, I understand this defensive bonus could be increased, even substantially, depending on how many wizard bubbles are protecting the target, but to overcome 1 lvl 4 wizard bonus, you would need at least 5 level 1 or 2s, or 2 lvl 3 or 4s and one other wizard, and honestly, who takes that many wizards in a normal game?
This bubble issue would bring up the whole all eggs in one basket that I thought a lot of people hate about 8E? If a player being introduced to the game sees all his flanking units easily destroyed by magic then why wouldn't he just concentrate all his units into a 12" radius bubble? This will make castling armies even tougher to target with spells. This will make deathstars even tougher to counter with spells. This will severely hurt high mobility armies that rely on redirection or flanking.
Another problem with the defensive bubble is that it makes it very difficult for an enemy to dispel enemy Augments on the first or second turns, depending on the type of Army. +4 to cast a remains in play augment on the first turn, and your opponent, who will most likely not be within 12" of the caster or target has only a +1, or a +2 if they have two lvl 3 or higher wizards.
Your spells, while flavorful, seem to be wildly varied in effectiveness, between lores and within lores. Maybe it's your wording, on some of the spells, but several seem almost useless. Other spells have casting costs 2 or more points lower than equivalent spells now, and those usually have another effect even better than the equivalent. This reduced casting cost, combined with the reduced dispel ability of an opponent really swings the magical balance. Your lore attributes are also wildy varied, with some of them being useless and others being completely devastating.
I think your free inclusion of the signature spell is a mistake. Not only does it technically increase wizard power by giving them one more spell, the signature spell is meant to be a tactical choice of the wizard. Some of your signature spells are honestly garbage, and some are way overpowered for what they cast. For normal 8E lores, the signature spell often gave a lore something that was missing in the rest of the spells. A wizard would need to decide which of his rolled spells would be less useful than the signature. It was meant to give flexibility, but also meant a possible sacrifice, especially for lower level wizards.
You put a lot of effort into this and it shows. If you are leaving it as it stands, I think you should clarify some of the spell descriptions and wording. As an outside party reading through it, some of the wording could easily be interpreted one way or another. If this system is meant to completely replace 8E magic, you should effectively re-write the whole chapter. You don't mention if failing to cast a spell (not meeting the casting value) prevents a wizard from continuing to cast. You don't mention if "channeled" power dice can only be used by the wizard that channels them (which was the case in 7E, this prevented other wizards from feeding power dice to the wizard with better spells). And so on.
If you are still gaining feedback and interested in changing things, I think you should revisit the balance between the lores. There are some that are very strong compared to others. Additionally, the inclusion of this magic system should come with an overall increase in the cost of magic users, since almost any Wizards would be more effective, with the lowered casting values given, and the ability to recast multiple Remains in Play spells on different targets. Lore of Metal and Lore of High Magic are hugely overpowered compared to some of the other lores, at first glance. On a 10+ destroy a magic item on an enemy character within 18" AND the caster gets a copy of that item AND you do D3 metal hits against an enemy unit? Even the Arcane Unforging from 8E needs a 13+ to cast and it fails to destroy on a 1, and it doesn't make a copy. Your Flames of the Phoenix is more powerful than Piercing Bolts of Burning and has a casting value of 3 less. If you are using spells and casting values from 7E, which it seems like you are getting a lot of inspiration from, you need to remember that 7E casting didn't add the caster level to the roll.