Wow. You're really... passionate about this...
I created that chests page maybe six months ago (yes, the zioth website is my website), and I regularly keep it up to date, because it's relatively new. Other pages, unfortunately, don't get as much attention.
Yes it does. Every time you get a drop, you get two of that drop. So on average, you will get twice as many soulstones with double drops.
The real problem with elite is that you're only going to get maybe 8 stones (from multiple levels) even with double drops, so it takes a long time to farm a hero.
Not sure where you're getting that. I've always seen what look like the same odds, no matter how many times I farm the same elite level. I've never seen any evidence to the contrary, from any poster on these forums. And those odds haven't changed since the PerBlue days. It was always one stone per three attacks on average, with the occasional lucky 2 stones or unlucky 0 stones.
You get 120 stamina for 50 diamonds, not 60, and I still don't know why you're saying double drop doesn't give you... double drops. Plugging the right numbers in, 42/2.4 = 17.5, or 15 for the lower levels. With double drops on, that's between 7.5 and 8.75 diamonds per stone. This is actually lower than it used to be, because GREE reduced the stamina cost of most elite levels. If I remember correctly, the highest Elite level used to cost 20 stamina.
You should read the section of the page which is specifically about the All Hero Chest, instead of just the summary on top. It goes into much more detail. I'll break it down here:
If you're specifically looking for the first bonus hero, then your best bet is to buy exactly 10 chests. This comes to 57.8 diamonds per stone. This is a worse deal than shops, and a much worse deal than Double Drop Elite, but it's slow. You'll only get 6-8 stones per hero per day, without resets. Now this 57.8 number assumes that you only want one hero. The more non-5* heroes you have, the lower this number drops, to a minimum of 17.95 (when you have no 5* heroes, at which point you can get a better deal by buying 35 chests).
If you need all three bonus heroes, then you want to buy in increments of 30 chests. Stones cost 33.92 diamonds each, which is a better than shops, but still much worse than elite (unless you're in a hurry). Again, this assumes that you only want those three heroes.
The 16.67 number is when you don't have a single 5* hero, and you buy exactly 35 chests. If you're WAY behind, and have a ton of heroes without 5 stars, then the All Hero chest is the second best way to get soulstones (after silver chests, which are essentially free, but only get you 1* heroes).
Like I said earlier, this isn't true. The odds were always like that with Elite, and I say that as someone who, like you, has also been playing pretty much since the beginning, and who's debunked a lot of theories on these boards regarding "fixed odds" (the most common is the one saying that Gold Chests are rigged because someone didn't get the hero they wanted after 50 buys or whatever). Elite has actually gotten cheaper over time, since GREE lowered the stamina costs at some point. If you can point me to any posts where people compare a large number of elite runs with PerBlue and a large number of elite runs with GREE -- posts with actual statistics, instead of just a feeling that things might have changed, I'd appreciate it.
However, even if the odds have changed, Elite is still mathematically better than any chest, again assuming you're not in a hurry. If you want soulstones quickly, All Hero Chest is the way to go.
Relax. It's a personal website that I maintain for fun. I'm capable of making mistakes, and I encourage you to correct my math if I'm wrong about something. I explained this particular VERY MISLEADING example above, but that doesn't mean everything on the site is correct.
Um... sorry? I only display chests that still exist.
To address the apparent source of your anger here, it is still my opinion that chests aren't worth it - that stamina buys and stamina resets are always a better deal, unless you're way behind, in which case hero chests are good (and fun! I used to buy them too, a long time ago)!
Can't argue with that. Even fewer heroes are in shops, which is why saying stones cost 40 diamonds in shops is kind of misleading.
Done. My numbers for Elite were a bit high, because they didn't take all of GREE's stamina cost drops into account. It should now be correct.
Those were fun, but they didn't last very long. I think that was PerBlue's last desperate attempt to stay afloat before they sold the company. I think I prefer consistent contests over flash sales.