What I say below is not intended as any kind of slight to Gobelure (or Elric), because Gobelure's key insight ("monster CR in 5E scales roughly as a 3/2 power of HP/DPR, and so does assumed player capability") is quite valuable. But the implications of that insight aren't what Elric is claiming they are.
If this were true, then Gobelure's system
would be unable to replicate the results of the regular encounter system when applied to creatures of the same CR, since it does not use an encounter XP multiplier. But this is not true, and one way to see this is that Gobelure's system does (pretty closely) replicate the results of the regular encounter system (with the multiplier) when applied to creatures of the same CR. His post lays out the math underlying why this is true:
http://www.enworld.org/forum/showthread.php?367697-Encounter-difficulty-how-to-fix-it
TLDR: It is unable to do so, and more importantly it diverges not just from the DMG system but from actual expected damage as number of monsters increases.
Gobelure's math isn't saying what you think it's saying, and it is in fact unable to replicate the results of the DMG system when it comes to scaling. (It's not even
designed to do so! Gobelure's focus is on solving the "three rats and a lich" problem, not the "three liches" problem.) It does not scale with the artillery equation. Illustrative example:
1 brown bear vs. 4 2nd level PCs: Easy (
200 XP/800) under DMG system, Easy (
2 TMEL/6 TPEL) under the EL system.
2 brown bears vs 4 2nd level PCs: Hard (
600 XP/800) under DMG system, Medium (
4 TMEL/6TPEL) under the EL system.
3 brown bears vs 4 2nd level PCs: Very Deadly (
1200 XP/800) under the DMG system, barely Deadly (
6 TMEL/6 TPEL) under the EL system.
You'll see this divergence any time a multiplier boundary is crossed. E.g. EL and DMG both agree that two demiliches at a time is Hard for 5 20th level characters, but EL says only one Demilich is Medium and DMG says it's Hard.
So when you say it "replicate the results of the regular encounter system (with the multiplier) when applied to creatures of the same CR", you're misunderstanding what problem Gobelure's system is trying to solve as well as the results it gets. It works pretty well, better than the DMG system, for creatures of
different CRs, but for creatures of the same CR the DMG system is IMO more accurate. Although neither system is very good at predicting actual results because they're both based on CR, which is a poor summary statistic of deadliness even before you toss it into simplistic equations. E.g. it values ranged and melee capabilities the exact same, doesn't account for mobility at all, treats abilities like regeneration as simple static HP inflation even for creatures with the smarts to use those capabilities tactically.
More importantly, not only does Gobelure's system diverge from the DMG system, it diverges even more from expected reality than the DMG system does. Take all those brown bears against, for simplicity, a party of four identical Str 18 2nd level Fighters with AC 18 (chain and shield) and battleaxes (+6/d8+4) who don't spend any Action Surges during the fight.
Accounting for crits, a fighter's expected DPR against the bear's AC 11 is 7.03, so it should take 5 fighter-rounds to kill a bear. The bear's expected DPR against a fighter is 3.63 for the bite plus 4.75 for the claws, so 8.38.
1 bear: The bear will inflict 8.38 on the first round, and then maybe (25%) inflict 8.38 on the second round depending on initiative, so 8.38 * 0.25 = 2.09 is the expected damage. About
10.5 damage will be inflicted on the fighters.
2 bears: Two bears will inflict 16.76 damage on the first round, then 1.25 bears will inflict 10.47 damage on the second round, then 0.5 bears will inflict 4.19 damage on the third round.
Total damage inflicted is about
31.5, three times as much as the 1 bear fight. This is the reality which XP multipliers try to reflect.
3 bears: Three bears inflict 8.38 * (3 + 2.25 + 1.5 + 0.75) =
62.85 damage on the fighters over the course of four rounds. Three bears is twice as deadly as two, and six times deadlier than one bear. The DMG system gets this basically correct (it breaks down a bit due to rounding at larger numbers of bears) by saying it's six times as much XP value but the EL system thinks deadliness scales linearly in the number of bears, so it's off by a factor of two when it says it's only twice as much EL.
Gobelure's system does what it is designed to do over a narrow range, but any time you scale number of monsters up significantly it will break. This would be more obvious if the DMG system weren't also scaled over a very narrow range, but any time you scale up from one monster to two or three the results will diverge from the DMG system because of that lack of multipliers, and it will diverge even more from the actual combat results.