To be honest I haven't followed all your graphs and calcuations; but if I'm understanding you right then this will be no surprise to anyone who has refereed higher level 4e.
I think it's pretty well known that, if the players know how to play their PCs, then an on-level challenge at epic tier will generally not be as proportionately challenging as at heroic tier.
Level +3 to level +8 is the range I tend to work in at upper epic.
EDIT: And our group doesn't use Expertise feats. A +3 to hit would obviously make the PCs even more effective.
I haven't looked into this thread as of yet and only briefly skimmed it now. But just lending my support to the above.
My last 1-30 campaign featured 3 PCs; Bladesinger, Rogue (Duelist), Hybrid Swarm Druid/Warlord. Each had a Companion character and one of them would play into each combat Encounter Budget, while the other two receded into the realm of color.
Upper Epic Tier workday was typically something like:
2-3 Combats @ L + 3 to L + 8 (with a stray one going a bit beyond that now and then)
3-4 Skill Challenges, majority C1 or C2 with maybe 1/4 C3. L to L +2.
Regarding standard Healing Surge expenditure in a level 30 combat, I'm not sure my data point will be particularly insightful for this thread. Combat-wise, the group's makeup was effectively:
Bladesinger - Sticky, mobile (tons of teleports including at-will) melee Striker with controller (small C) secondary (lots of forced movement) but burst Controller (big C) capacity. Defender level passive defenses (all) with tricked out SW and multiclass Fighter stuff. Nearly perma-Bladesong (I want to say it was refreshable...5 times/day...at that point). Tons of Minor Action MBAs, tons of off-turn actions including devastating OA ripostes, and immediate actions to ramp up the defenses further. Turns into an insubstantial dragon spirit with max HPs when PC dies and can turn into an actual dragon as a Daily.
Rogue - mobile (tons of shifts) melee Striker with near Defender AC/Ref (and solid Fort/Will), but the ability to ramp that up to well beyond Defender with riders and a very large suite of immediate actions (and THPs to boot). Several Minor Action attacks. Force multiplication MBAs through (I think 1...maybe 2) a few powers and Action Points (multiclass Bravura Warlord).
Druid/Warlord - extremely beefy Leader/Defender/Controller hybrid. Force multiplication and summon Dailies (obstacles/control), suite of encounter CBs and CBLs w/ control riders, great soak, off-turn saving throw enable, 4 encounter-based heals.
The group had a lot of versatility in combat so its hard to pin down a precise M.O. Lots of enemy funneling into bad areas for Forced Movement into hindering terrain and/or hazards. Lots of MBA enabling of the Bladesinger. More of less no good choice of targets for enemies (all stout, resilient, 2/3 mobile). Typically 1-2 Standard Actions spent on Terrain Stunts for AoE (or single target control rider).
Anyway here is a single anecdote as best I can recall (it was around 2 years ago).
1) Second combat of the day (4th total conflict with 2 preceding SCs), leading up to the final showdown at the bottom of the Abyssal Sea with Dagon.
2) The Companion character used was the Druid/Warlord's Bear which was a Leader/Soldier hybrid.
3) Wave-based encounter (3 waves; initial, round 3, round 5). Tons of Swarms (splitting into Bloodied Standards at Bloodied), protected Artillery Minions (protected by Y Axis, blocking/hindering terrain, Hazards, and the Swarms), protected level 30 Solo Controller (Leader). Tidal Eruption Hazards which would leave Hindering Terrain (Styx-tidepools). Total encounter budget was L + 12 (again, somewhat mitigated by wave-paradigm).
The Bladesinger turned into a dragon and flew around the massive Abyssal cavern strafing enemies with a CB5 Breath Weapon. He eventually "died" and turned into an insubstantial dragon spirit with his full HPs (this was intentional by the PCs, for the drama and to trigger insubstantial and turn the Bladesinger into an OA meatgrinder with only half-damage coming in) and spent 6 Healing Surges while mitigating a huge amount of damage due to Insubstantial.
The Druid/Warlord, a Summoning, and her Bear companion engaged the Swarms. She soaked a ton of damage with her +5 Con damage reduction throughout the course of the fight. She spent 4 Healing Surges using her level 30 ED ability (spend Surge when you reduce non-Minion enemy to 0), and probably 2 others along with going through a chunk of THPs (given by Bear MBA rider). She also had Weakness up for a bit to mitigate a large chunk of damage.
The Bear Companion spent 2 Healing Surges, a chunk of THPs (from Druid) and eventually was taken out.
Meanwhile the Rogue used his Dark Road Epic Destiny Feature (and a successful High DC Dungeoneering check) to locate and traverse a Planar Anomaly, letting him get up to the Y-Axis protected Artillery Minions and Solos. He does his SA damage without a flanking ally so this was SOP. His suite of activatable defenses, high passives, and level 21 ED feature (-4 to attack him for rest of encounter after level or less creature hits him) let him keep the Controller busy until the cavalry arrived (both he and the Controller nearly taken out) to finish the deal. He probably spent 4 Healing Surges and went through some THPs.
So that is probably something like:
* 18 Healing Surges
* Full HP to 0 for 2 of the 4 characters (Bladesinger "died" activating his ED feature and the Bear taken out)
* Probably 300 (maybe more?) damage soaked from straight damage reduction and THPs.
* Large number of real action denial or effective action denial (through deployment of IAs and/or negatives to hit from status effects or features).