Ok lets go at it again step by step so tjat you can follow.
PCs are in a corridor. They open a door and six ogres are in a big room. Big enough for a few more persons to get in.
Ok sure, let's do this-- I have tomorrow off.
Six ogres? A mighty big "room" but ok, especially with "enough room for a few more persons to get in." If that is all the extra room there is, those ogres must be feeling pretty darn cramped IMO.
Anyway...
Initiative is rolled, and a few attacks are made, one PC takes point and block the doorway. This is a standard tactic after all.
A few attacks by who? The PCs? Six ogres against a party of what? Party consistency is part of the picture as well. Let's assume a party of 4, so you have the 1.5 to 1 ratio you mention. Even at 6th level, 6 ogres would be a
deadly encounter, regardless of tactics. At 7th, it becomes hard, at 8th moderate, and finally easy at 11th level. So, let's make it "hard" and say the PCs are 7th level.
As to blocking the door: the players are idiots IMO. That is the worst thing they can do. They stay in the corridor (typical D&D 10-footer?) so only one ogre can approach the party at a time. You let the
ogre block the door so the other ogres can't get at the party.
One ogre approach, and tries to grab the high ACed PC. For the sake of convenience the ogre wins the grab.
Sure, even in the corridor your tactic of the ogre grapping one of the two PCs on the front line could happen. You suggest the "high AC" PC, so if this
is a front-liner, let's assume proficiency in Athletics and STR 16, so +6 vs. the Ogre's +4 for STR only. The ogre would have about a 38% chance of winning in the grapple attack, so there's a decent chance it will work--benefit of the doubt.
With the PC in hand, the ogre turn around, and release the PC in the room.
That isn't how it works. The ogre can move and take the PC with him, but unless he actually
moves, the PC isn't moved either. But, for discussion's sake let's agree the ogre drags the PC back into the room where other ogres are waiting. Well, an ogre can move 40. So, if it moved into the corridor, it will likely have maybe 20 feet of movement left. Dragging the grappled PC halves movement so the ogre can only go 10 feet--not very far--assuming it can move even that much. And of course the other front-liner PC will get an OA (give that PC a hit and Sentinel and the ogre isn't moving
at all 
).
Now the other ogres close in, and three attack with a +3 to hit. The last ogre pushe out the room and attack the othe PCs.
So, the other ogres surround the PC (you're right with their reach of 5 feet, only 4 ogres could be in position). The grappling ogre isn't doing anything, so the other three attack with +3 to hit. Given this is the "high-AC" PC, at best--even
with +3--each has maybe a 50/50 chance of hitting.
shrug
Round two.
One ogre us down or not but our PC is now attacked by two ogres and two other ogres are using the help action to guve the two other advantage on their attack. So the two attacking ogres have advantage and an additionnal +3 to hit with your method. Which is way better than a simple advantage (which are not supposed to stack). So now, they can fairly and reliably hit our high level PC because they now have the equivalent of +8 to hit (advantage is usually considered to be +5). Whereas with the normal method, they would be attacking with advantage.
Ok, so you are trading 1 normal attack at +6 and 3 attacks at +9 for two attacks at +9
with advantage. Fine. Let's do the math. We'll assume the PC has AC 20 (reasonable for a high-AC PC at level 7 IMO).
Scenario 1: one at +6 and three at +9: expected damage is 25.85 per round.
A (+6): 0.3 x 13 + 0.05 x 22 (critical) = 5
B (+9): 0.45 x 13 + 0.05 x 22 = 6.95 x 3 = 20.85
Scenario 2: two at +9 with advantage: expected damage is 21.255 per round.
(+9): 0.6525 x 13 + 0.0975 x 22 = 10.6275 x 2 = 21.255
Scenario 3 (RAW): four attacks at +6 with advantage: expected damage is 33.54 per round.
(+6): 0.48 x 13 + 0.0975 x 22 = 8.385 x 4 = 33.54
So, of course RAW has the highest damage at 33.54, but you seem to think two ogres "helping" while only two attack will be more deadly than if
all four attack? No, giving a couple ogres advantage by helping is a losing strategy for the ogres--but then again, they aren't too bright.
If the poor sod tries to dodge, then two of them will still have +3 to hit (two ogres would use help action) whereas with the normal method they would either all attack with disadvantage or two of them of them would attack with normal chances to hit with the two other ogres would take the help action.
Scenario 3 (RAW) is easy: 20 points per round expected. (All with advantage cancelled by the Dodge action gives 5 expected damage per ogre).
Scenario 1: all attack with disadvantage: expected damage is 11.4325 (44% of the non-Dodge expected damage)
A (+6): 0.12 x 13 + 0.0025 x 22 = 1.615
B (+9): 24.75 x 13 + 0.0025 x 22 = 3.2725 x 3 = 9.8175
Scenario 2: two attack as normal (helping cancels the disadvantage imposed by dodging): expected damage is 13.9 (65% of the non-Dodge)
(+9): 0.45 x 13 + 0.05 x 22 = 6.95 x 2 = 13.9
So,
if the PC decides to dodge,
then the ogres helping each other will work out better, but whether or not it is a good strategy for the PC depends largely on what the other three PCs are doing. Either way, the PC will live longer with the reduced damage and if the PCs move into the room they are actually now flanking a couple ogres (if the surrounded PC is attacking, that is...).
I will stress that it is the monsters that usually benefits the most from flanking as they usually outnumber PCs at a ratio of 1.5 vs 1. If course, this depends a lot on the CR of said monsters and characters' levels. But at mid level, 1.5 vs 1 is fairly common.
Well, of course, but that is pretty realistic isn't it? To have a game where having extra numbers in battle isn't a contributing factor is pretty poor design. I agree for many tables advantage is too strong, so my idea offers a method where numbers can still matter, but not as much as normal flanking would.
Anyway, also with my idea you would need a large number of allies to come close to giving you the same increase advantage does. Given the numbers above, of a 6-4 battle, if things happen to get "spread out" more evenly (2-1, 2-1, 1-1, 1-1) then two ogres would get a +1 and that's it. Not as big a deal, is it?
