This is why I tried to show a more reasonable example, as opposed to throwing around your entire stable of top-level spells with an oddly multi-classed character. I agree that compared to other top-tier evocation AOE spells vs. multiple targets, I think CME may not turn out too extreme in actual play. But where it completely blows away other spells is in single-target damage with spells that have a ton of attacks.
Here's a bog-standard 11th level druid and wizard, each using their single 6th level spell slots in one round:
To put this in perspective, casting fireball as a 6th level spell is an average 49.5 damage (with a save for half). It's AOE, so ideally you get 2 or 3 targets - we'll say 3 targets for 150 damage. That's still far less than the 244 average damage from the 6th level magic missile (that cannot miss) empowered by CME, and which you can distribute damage much more evenly and effectively. And the level 1 MM comes out pretty amazing as well - with about 1/3rd of the damage for 5 spell levels lower!
Granted, this combo takes two 6th level spells, and the druid could cast cone of cold at 6th level (9d8 avg 49.5) + the wizard's 6th level fireball, and if they both hit at least 3 targets that's ~300 damage instead of 244 - which makes CME seem pretty reasonable compared to large AOEs that hit many targets. But the cone and fireball are tactically situational, requiring targets to scale, and still doing a low(er) max to each individual target. The CME+MM combo does 244 avg damage to anywhere from 1 to 8 targets, and needs no situational targeting to reach maximum potential. It's not so much that the potential damage upper total is comparable, it's that you can do all of it to a single target. Even 6th level disintegrate only hits for an average of 85 damage (10d6+40) against a single target (and that target can save for zero damage). I don't think anything else can combo for such a tremendous single-target hit at that level.
And scorching ray is the exact same thing. In that case: 6th level SR is 7x2d6 + 7x6d8 = 14d6 + 42d8 = 294 avg damage, with the biggest difference being that you have to roll attacks for each ray. That's pretty close to a 5.0 ancient white dragon's total health (CR 20, 333 HP), for example - for two 11th level casters in one round.