Hopeling

Ooh, very interesting.
I'm not certain I understand what this equation is telling me, though - your example gives .29, does that mean it's 29% uptime on average? Does the spacing of the procs in that chain matter?

If you're running trials, definitely. Or in Dark Astoria, also definitely.

If he doesn't want to team for the WST, though, I'm guessing he doesn't want to team for trials, either.

I'm counting 216 for a T4, if you already have both T3s. With only one T3 you'd need 12+20+96+216 = 344.
You can cut down on the t3/t4 numbers a LOT if you're willing to run the WST, because building Notices from shards is horrible. I don't know how dedicated you are to soloing your way through this, though. And, as mentioned, Dark Astoria will help.

This wasn't a well-guarded secret. It's near the top of the paragonwiki page on HOs, for example, and came up regularly in any forum thread where HOs were used. Enzymes say "defense debuffs" right on the tooltip, and Active Defense doesn't list defense as one of the enhancement types it can take, and Mids actually doesn't show HOs affecting Power Boost at all. Noticing any of these things might lead you to do a little digging on what's happening, which would probably lead you to the aforementioned wiki page.
Without the ability to predict the future, I can't say for certain they won't. But it's not terribly likely, and it certainly wouldn't be a comparable change to this one, where we have literally had years of advance warning.

They did It's changed on beta now - 5 fury ever time it procs, 7 for the superior version.

In terms of the inf needed, it kinda did

Any given amount of -tohit is equivalent to the same amount of +defense, yes. There are two caveats here:

1) Tohit debuffs only help against debuffed enemies, obviously, so Time's Juncture doesn't help against the guy shooting you from 50 feet away
2) Tohit debuffs are equivalent to the same amount of defense as the debuff that actually gets through, which is NOT necessarily the same as the debuff you apply. Against an enemy your own level, your 10% tohit debuff acts just like a 10% defense buff. Against a +4 enemy, the purple patch reduces your debuff to .48 of its normal effectiveness, or -4.8%, so it's as good as 4.8% defense. A level 50 AV has 85% resistance to tohit debuffs, so against them it'd be worth 1.5% defense. If you're fighting that 50 AV and you're level 46, you get hit by their AV resistance AND the purple patch, so only -.72% of your debuff would get through, making it as good as .72% defense.
On the other hand, being above your enemies would make it more effective, such as when you're running around with a level shift fighting level 50 enemies.

-Res procs are actually not very good in AoE attacks. Worse than a regular damage proc, for most uses. I personally favor the Force Feedback proc. The Armageddon proc is a decent alternative, if you're not already using it somewhere else.
Edit:
Presumably, it would get a chance to fire every 10 seconds, like any proc in a toggle does. I haven't personally tried it in that power, though.

That's true, but you can get Temp Invuln with PBU, and negative/toxic damage aren't so common that it's a major advantage to Soul Mastery, IMO. What IS a major advantage is that Power Boost has half the recharge of PBU, so you can use it for more than just Farsight. You could pop it almost whenever you want, for your heals or hold or a defense boost from your toggles or whatever you want, and it will probably be back up before you need to recast Farsight. On the other hand, it doesn't have a damage boost.

Mids is wrong about both Stalker and Scrapper EPP attacks, and in the same way - it adds all the crit damage together, including the guaranteed hidden crit (yes, even though scrappers don't have Hide). If you mouse over the damage, it shows how the damage breaks into its component hits: unslotted, it does 62.56 damage, plus a 5% crit for the same amount, plus a 10% crit for the same amount, plus a guaranteed crit for the same amount, plus the DoT. This all adds up to the much-too-large figure of 154.5 damage.

In reality, Scrapper Fire Blast deals 62.56 damage, and a 5% or 10% chance (depending on target) for another 62.56 damage, plus the DoT. Against 10% crit targets, this means its average damage will be 62.56 + .1*62.56 + 4*6.26*.8 = 88.8, and so its DPA will be 61.19 with Arcanatime. This is nearly identical to Scorch's base DPA (61.3), but Scorch costs less and also casts more quickly, and therefore benefits more from procs like Reactive. The difference between the two chains will be small, though, and there are occasionally some benefits to having a ranged attack that don't show up in an attack chain calculation, so you'll probably be fine either way. If you're short on slots, the all-melee chain only needs you to slot 3 attacks instead of 4; on the other hand, maybe you want a certain set bonus from Fire Blast anyway, and you do still need it for Fire Ball.

"Except when we have a good reason not to", such as one of the Stalker combos being tied to a power on a 90s recharge.

"This is a rule we always follow except when we have a good reason not to" isn't much of a rule, frankly, except maybe as a rule of thumb.

I'm pretty sure, but not positive, that it will overwrite/refresh the duration.

I'm not sure if I like the OP's idea specifically, but swapping which powers are part of which combos doesn't break the cottage rule. Look at the recent EA changes, for example - the set's heal got moved to a completely different power (it was removed from Energy Drain, and given back with Energize replacing Conserve Power). Even a change this dramatic was apparently not a violation of the cottage rule - or, it was, meaning even the devs don't mind breaking the cottage rule sometimes.

I kinda think the Brute/Tank/Scrapper combos are OK as-is, or at least not horrible, but the Stalker ones could definitely use a change.

If you have Musculature, 4 Smashing Haymakers will ED-cap your damage. If not, the 4 Haymakers plus the Mako quad will. If you need more acc, end, or rech the triple is nice, but many attacks can get by without it.
Careful with that calculation - that's how much the proc is worth when it goes off, which is only 20% of the time. Since the proc rate is the same as most IO procs, you can compare that value directly to the damage from, say, a Mako's bite proc. The Achilles' Heel pretty much always comes out ahead in that comparison, by a wide margin, so it's better than a damage proc. To figure out how much it does for your chain as a whole is a bit more complicated.
As a rough estimate, you can pretend that the proc is a constant -4% resist, which is reasonably accurate if you use the attack with the proc about once every 10 seconds. So if you do 150 DPS without the proc, you'd therefore gain ~6 DPS using the proc, according to the rule of thumb. Using the proc more often will see a larger gain (but with some diminishing returns, since it can't stack), and less often will be a smaller gain.
Other than for hunting Jurassik and similar negative-vulnerable foes, I'd use the Mako proc instead, personally. Lethal resistance is much more common than negative resistance, but not by so much that a negative damage proc's average performance is better with a 1/4 lower proc rate. If you deal lethal damage yourself, it might be worthwhile to use the ToD proc, to hedge your bets a little against lethal resistance. You can also consider damage procs from your secondary effect sets - Touch of Lady Grey has a better negative proc than ToD, Explosive Strike has a smashing proc which is less resisted than the lethal from Mako, etc.
Don't get me wrong, StJ is a good set, but being able to land one really big hit with damage buffs on a heavily debuffed target, using the AT designed specifically to land one really big hit, doesn't make it broken.
Ah, I see - reading comprehension failure on my part.
Yes, pretty much. -3 hp/s regeneration is equivalent to +3 DPS, in terms of killing things, and a DoT interface adds way, way more than 3 DPS.

He posted once that he had discovered a way to do so, but soon thereafter posted that it didn't work after all, and would require further investigation at a later date. It was never addressed again after that, and certainly never made it to live.