Hello, as it is lore master class is very powerful for mundane characters but it has very poor synergy with casters, which I believe is a bit unthematic.
Lore master requirements are:
8 Lore - almost every build invests in lore anyway
16 int - Most builds will have 14 int anyway, so it means they just need to give up 30 HP and 1 fort save by reducing their constitution by 2. Con saves are already the highest save for most so losing 1 doesn't matter really. And they can just use a lesser secret to get back the HP they lost.
SF: Lore - A feat tax for everyone but I'd argue a high lore score is more beneficial to non-casters. And builds with fighter levels tend to have more feats to spare.
Prerequisites aren't very taxing for melee or casters, but I'd say they are very light for a fighter compared to a cleric or sorcerer.
The class benefits are also very tailored towards melees. Bonuses for wands and scrolls for casters do not matter much since casting from their spell book will be better most of the time, except buffs like zoo spells to save spell slots.
There are no lesser tricks to improve their casting or make up for the caster levels, or bonus class feats they lose (assuming they'll need a discipline dip they lose level 26 and 23 bonus feats depending how deep they go), while melees get 1 ab and 1 ac. Which stacks with armor skin or epic prowess so they are pure bonuses, not making up for anything lost.
I think adding a lesser secret that increases their caster level against dispells by 2, and one that increases their caster level by 1 directly. Perhaps another one that has like a spell-clutch effect could be fun, and make the class more viable option for caster.