Hopeling

Most powers, even attacks, can obtain sufficient enhancement value with 5 slots or less. This means you can often slot a proc and give up nothing you'd miss. Don't go overboard on this - most attacks are best with either zero or one procs.
The Achilles proc is 10 seconds of -20% resistance. Figure out how much damage you'd do in that 10 seconds, multiply it by .2, and that's how much damage the proc effectively deals. It's not a dramatic difference, but it is significant.
I'm not sure what you mean about StJ, it's no more broken than any melee set, and dramatically less broken than, say, TW or SS.
If you're limiting yourself to S/L only, probably not possible, because that rules out /Fire or any damage aura. GMs have huge regen, around 300 hp/sec for the higher level ones, if I recall, which means you need to do 300+ DPS to make any progress at all, and far above that if you want fights under 10 minutes long.
If your definition of "soloing" includes inspirations, Lore pets, and/or easily-obtained temp powers (Envenomed Dagger), this admittedly becomes dramatically easier.
Incinerate-Scorch-Cremate-Scorch should be a superior chain to the one you're using, but not dramatically so. You can build a decent chain (like the one I just named) without the single-target sword attacks, so those are skippable if necessary, but I would hate to skip Fire Sword Circle. Your concept is your concept, though.
Degenerative's -hp is basically trash against AVs and GMs. It caps at -150 hp per stack, making it far weaker than Reactive's res debuff, and either will be weaker than the Reactive DoT for all but the most extreme (and extremely expensive) builds.

For 8 seconds, yeah. Then you can try again. Or you could use the Nemesis Staff (or any other KB/KD/KU power) to knock them down.

If the queue behavior for iTrials can be extrapolated to other things, the queue seems to wait something like 90 seconds after there are the minimum number in the queue, and then launches with however many people it has. So if 100 people queued up for "First Available" all at roughly the same time, you'd get a bunch of full or nearly-full teams. If they queued up individually over the course of an hour, you'd get smaller teams, although not necessarily all minimum size. Which TF they'd end up on might be some default value (Posi 1 would be the most obvious, but it might also choose the first alphabetically, or the highest-level TF they're all eligible for, or some other criteria), or maybe it would choose randomly, depending on implementation.

[Citation Needed] on those numbers, for one thing. If you're correct, though, then the inf sinks only need to be attractive to that 10% of the playerbase. Like, say, an increased auction inventory for 100m per slot. Most players wouldn't use that or even especially want it, but serious marketeers might.

I wondered how long it would take for this argument to pop up.

Why does an invulnerable stalker make any less sense than a regenerating stalker? Or an electric stalker? Why can someone with tough skin not learn how to Hide?

Here's a better way to deal with this problem: if the power set doesn't make sense to you, don't play it.

According to the patch notes, that's exactly how it works. Admittedly, I have not tested it myself.

You're right, sorry. I made my point, I'll shut up about it.

I personally don't really think of a recipe that goes for 10m or less as high-end. More like "standard issue on every IO build". Indeed, all of the powers and procs you listed (except Physical Perfection) are standard issue on pretty much every /WP - I would argue that your own build (which you admitted made sacrifices to reach the softcap) is the exception here.

Nobody's arguing that TW doesn't cost a lot of end, or that you shouldn't design your build with that in mind. But you specifically said that it required you to have more recovery than /WP can provide, and that every tool at your disposal still would be far from sufficient. Both of those things are just absolutely not true.

Invincibility is possibly the most important power in /Inv other than Unyielding. Trading it for Hide would gut the set. (Willpower also traded RttC for Reconstruction. Hide replaced QR.)

Based on the other sets Stalkers have, it's much more likely one of the passives would be dropped (or rolled into another power) for Hide, and then Invinc would probably change to be something other than a taunt aura. It might also change to a static bonus instead of a scaling one, like Entropy Shield.

This is like the time someone in help chat said "It's 4am here", and someone else replied, "no, it's 7am here!"
Hint: Screens come in more than one size.

I've never seen my Ion miss - this should be easy to test, actually, lemme go find a MoG Paragon Protector.

Yes, we do!

It has considerably more than a tenth, and costs the same as either of them individually, not more than both combined.
It... is. It's far superior to Sprint alone. You don't get SS nor SJ by default, you have to spend power picks on them.

I did like the idea of an additional option for a purely cosmetic toggle, though.