I see two problems with your example. The first one, is that a combat does not need with a PC dead to be "a threat" or "meaningful". indeed, the CR system implies that the PC *win* the battle, but they lose a few resources in the process. A game where the PC have 50% chance to win an encounter is not balanced, is a game with 2 encounters length on average.
Certainly, I agree with all of that. However, I'm not sure that your objection is particularly meaningful in this instance, because the odds are good that, in one-on-one combat, a single 5th-level Fighter will come out nigh-unscathed against a single ogre.
I mean, you see [MENTION=6694877]slobo777[/MENTION]'s post where he sends 3
1st-level Fighters against 3 ogres, and they win more often than not? Now, add 4 more levels (with the attendant improvement in to-hit bonuses, hit points, combat superiority dice, and gear) and make it a diversified party (so that you have things like magical slows, walls, sleep spells, blessings, etc.), and I think you'll agree that even 3 ogres at once isn't going to be particularly challenging.
And if it is not particularly challenging at 5th-level, there's no way those ogres are holding up as a meaningful threat at 10th-level. Not yet, anyway.
The second problem with your example is taht you are using *one* ogre.
That was the example given, and the claim was that "an ogre" would be a threat to a 10th-level party.
I think that's been pretty conclusively disproven.
Would 12 ogres be a threat to a 10th-level party? In large part, I think that will be determined by how exactly bounded the accuracy system is, but given the way D&D has shaken out before (e.g., a proliferation of area effects in the hands of the spellcasters) combined with what we've seen so far (e.g., fighter superiority dice progression and rogue sneak attack progression), I'm no so sure.
A second ogre hitting the all-parry fighter pose a much bigger threat. At level 10, 3vs1 ogres can also pose a threat.
Sure - but the chances that both ogres hitting the fighter in the same round is only ~1 in 10 or 1 in 8. Against a solo 5th-level fighter, you'd expect one of the ogres to be dead before that happens.
And remember: posing a threat does not mean the NPC have 50% chance to win and kill the party.
Certainly not - but "50% chance to win if I play absolutely braindead" is not a meaningful threat, either.
If the ogres die, and drain a meaningful part of the party resources, then they are properly designed.
My supposition is that, so far, it doesn't look like they'll be draining a meaningful amount of the party's resources -
at 5th-level, let alone 10th.
If the fighter's
by himself against an ogre (and parries all the time), he's taken about 9 points of damage, on average.
And while it's likely that there will be more ogres fighting the 5th-level party, the fighter's not going to be by himself, and he's also probably going to have better gear or attack bonuses or defenses than I've assumed in my rough-justice numbers - and, afterwards, he's got the level 5 healer to patch him up (and maximize his hit die rolls).
Do "I cost the enemy a single Hit Die" or "I cost the cleric a single healing spell" represent a "meaningful" threat? Not in my book.