The effect of third-caster progression is basically to make you use utility spells or buffs, and maybe the occasional AOE against large numbers of low-level opponents. Something like darkness or gust of wind can still be useful at 7th level, but Agannazar's scorcher probably won't. That's also why abilities like Divine Smite are so strong: they let you add damage that automatically hits (or rather where the hit has been determined before the resource expenditure) and doesn't cost additional actions. Compare using a 1st level spell on Divine Smite (average damage 9, no action cost) and on casting magic missile (average damage 10.5, uses an action).I think it's a difference of perception. I see this as supporting my case: the EK should have the option to forego killing stuff to cast a spell that will be effective, form time to time. There's just no incentive to do so with the third-caster progression.
That's one of the reasons I like the swordmage idea so much: it integrates magic into the fighting, providing level-appropriate magical effects in an overall martial package.