Spellbooks should be like other weapons, where they degrade and drop on death, with good spells or higher damage numbers from good ones. Then reagents being cheap will be fine.
And then they need to do some things to make mage more viable at PVE.
If they create a wand/staff, that has a projectile left click attack (scaled appropriately), which is also required for casting this would accomplish what you've said, and I would totally be for something like this. The ability to left click a projectile that could be used while moving or in between parrying would make pve more similar to what FF do currently. (Obviously if its a wand you'd have to have a shield to parry)