70s during the day, mid-40s to low-50s during the night

Are you camping or hiking because that's an awful lot of clothes for such mild temperatures if you're going to be hiking.

It will be about two days of hiking and then about 4 days of mostly camping and walking around (mild walks).

Not sure what you'd need the mid layer for, even if you ran cold. The base and wind jacket should be more than enough for the 70s hiking, and then your Eldo (though I know nothing about the Eldo) for hanging around camp at night and sleeping in if necessary.

Eldo is basically a Thermawrap, but with pockets and filler like Thermawrap Parka.

I'm a desert rat that shivers when the temp drops below 75F (no exaggeration, i really do! conversely I only think it's a 'warm' day if it's over 98.6 and 'hot' is over 108) and I think you have more than enough/too much warmth. Your temps are basically our milder winter days and I find that usually just a light softshell works down into the mid 40s at night with no problems.

If you were looking at temps in the 30s I would say the eldo would be warranted. If you do run cold (even colder than myself), just wrap your sleeping bag around you and you'll be fine.

I see… Frankly, I was just going buy the chart here – http://www.backpackinglight.com/cgi-bin/backpackinglight/forums/thread_display.html?forum_thread_id=9378

Overkill?

Hardly. The location/region and weather variability come into play too and I carry a similar kit for that reason. There is no more than one extra layer really. I find mid layers really handy, and great for extending the range of a sleeping bag. The mid layer with a windshirt works great. My personal preference is for a slightly lighter fleece mid-layer, but we're quibbling over 6 ounces at most.

If you run cold or you want the versatility, why the heck not? I'm of a mind that any good UL kit can afford one item out of the "approved" norm. Some like a book, others a fat sleeping pad, etc.