Back on topic:
Classes are balanced around their combination of skills and spells (hereafter called Kit).
Some classes have very defensive kits- The prime example would be healers. They are balanced around the fact that they have very easy access to a large amount of positive spells. They pay for this in lack of consistent offence and a high degree of spell up-keep.
Warriors are a very obvious example of an offensive kit - other than their natural defences, they have nothing that can be clearly defined as defensive in their kit. This is balanced by having very high melee output, access to all weapons and reliable forms of lag.
Using hypothetical numbers we could say that a classes Kit should be worth 10 points.
Lets say that a Battlemage's kit has 7 points in self cast buffs, 1 point in melee skills and 2 points in offensive spells. (Yes i know I'm pulling the numbers out of my ass - this is to demonstrate a point - not to this specific example.)
If a Warrior is balanced to a Battlemage is also needs to have a Kit worth 10 points. Lets say a Warrior has 1 point in defensive buffs, 5 points in melee output and 4 points in offensive skills.
This is hypothetically balanced - although you'd need to do some analysis on what constitutes a certain point score in any 1 area.
What has happened consistently over the last few years is that QoL changes have been put in place that improve access to defensive buffs. You now have a situation whereby:
Battlemage: 10 point kit.
Warrior: 10 point kit + 5 points in Defensive buffs via consumables.
This isn't balanced.
Grim is suggesting that we increase the quality of Self-Cast spells to bump (in this example) Battlemages up to 15 points. The problem with this is that while it looks balanced on the surface - when warrior's don't have those buffs up them they are suddenly at a big drop. While this was planned for in the original design, pushing self-cast spells up totally unbalances things, and runs the risk of pushing casters up to much.
There are different ways at looking at balancing things, but personally i believe that inflating stats to balance other inflated stats causes more problems than it fixes - if nothing else it can reach the point where the whole engine needs a recode, rather than a few spells / skills need tweaking.
I'm of the belief that while each individual QoL improvement that was added wasn't a big deal, we've reached the point where as a collective, there is to much access to defensive buffs for classes that can't cast them. Between new pills that were added, new herbs that were added, spell forging, USEable items that bypass class restrictions there is just to much available for classes that were balanced around not having these things.
If we want to balance we need to go through the Affects list and have an honest conversation about what is essential, and what is nice to have. Buffs that are unique to a small group of classes via their Kits shouldn't be available via consumables - unless the consumable is self is restricted, i.e rare consumables, or class restricted consumables.