I actually feel that the very fact that this system has been playtested and played extensively is evidence enough that it works for some campaigns, and this is very much that kind of campaign. I don't really feel that this discussion is making any progress, and that it shouldn't be in this thread anyway. I'll write a last answer here for some of the more technical differences and then I'll leave it at that.
The randomness of this system seems unlikely that characters will survive for very long. All it would take is one lucky attack roll for the NPC and one unlucky defence roll for the player .
[sblock]Well, you usually have to be very unlucky and he has to be very lucky, and it's a small chance that it'll happen too soon. The risk of the attacker rolling 18+ and the defender rolling 3 or less is less than 1/40, and even then it's in no way sure that he is killed if wearing armor.
You're not supposed to take on vastly greater numbers than the party, and this system definately puts CR out of the question for determining encounters. However, I won't create encounters where you have to fight fifteen first-level tiraks - I might create encounters where you can, and where you will if you act stupid, but combat will be less slaying five orcs per round and more carefully ambushing the leader of the group.
If you want to kill many enemies at a time, make ambushes and traps. Create an avalanche or trap them in an alley with five hired archers in the windows.
More tactics.[/sblock]
Firstly, don't forget that while the barbarian rages his AC drops by 2.
Ah, yes, forgot about that. You're right, when raging you're more likely to take damage.
Not to mention, that you were comparing a 1st level wizard to a 6th level barbarian (with a higher Con). Since the stat pool that is given is the same for all players, I would imaging that for both the barbarian and the wizard the second and third highest stats would be given to Dex & Con.
[sblock]Well I think we have different play style, due to different focus between "role" and "playing". Also, if it's point buy rather than arrays or dice, a wizard usually opts for higher intelligence than a barbarian goes for strength, so there'll be less points to invest in other skills. And the barbarian's had a +1 to a score due to being over level 4. So in my usual groups games, those stats are albeit counting low quite the propotions they usually are.[/sblock]
Also, melee classes should be given more Soak points in order for them to survive as they will constantly be the front liners.
[sblock]
If they're constantly in the front lines of big battles without taking the toughness feat and/or wearing heavy armor, then they are doing it wrong. And they do take less damage than a wizard due to higher defense rating. There's no logical reason for them to generally take less damage from a stab, other than being better at avoiding it or "rolling with the blow", something that is represented by defense. Barbarians get it a bit, via DR, though that isn't going to be relevant in an E6 game since it's at level 7.
In E6, 6th-level barbarians has access to a special feat which grant them this ability, but since DR x/- and soak is about the same thing, it's more like allowing an extra level of toughness.
I could if you want swap it so that you get DR 1/- (an extra point of soak) at level 5, and that Improved Uncanny Dodge is their capstone feat instead (requiring Barb level 6).
A fighter type should invest some of his feats in Toughness, to do exactly what you are looking after. If you look at the GnG rules, Toughness now gives Soak 1 instead of 3 hit points.
And on low levels, I'd say you're less likely to get killed. The risk of getting that 18 vs. 3 situation is about as likely as getting hit by a critical hit (considering 50% chance of confirming threat) with an orcish spear, that's 3d8+12 damage (average 25.5 damage), and 25 damage is far more likely to take out a 2nd-level fighter in RAW than 21 (1d8+18) is in GnG (supposing the defense 3+x and attack roll 18+x), especially since any character focusing on melee should have at least 4 soak. For higher level chars in D&D, the orc stops being a serious threat, partly since players have high AC stopping the confirmation of the threat and partly because an orc has 5 hit points. GnG makes the orc always stay a threat, and that isn't a flaw with the system - it's part of the point of the system. The players will advance with levels, becoming stronger and stronger, but the level itself becomes a less bit important - other rewards will be handed out instead, such as high-quality items and not to be underestimated, things like land or power within a guild and such things.
[/sblock]
tl;dr:
I think the mistake you make is assuming that combat will follow the same pattern as in regular D&D with a few PC's pitched against a horde of lame-ass kobolds or against a giant dragon. Most combats here will be the PC's against a few other humanoids, sometimes more and sometimes less than the PC's. Monsters are special encounters that should be feared by the player, and if an ogre comes along you usually run rather than face it if you don't have to, even if you're level 4. It's a very unecessary risk that might not be worth the gold necklace it wears. If you don't like risking death when in close combat, play a character that doesn't frequent the front lines. Also, if you like high-powered, combat heavy, rolePLAYING, this might be the wrong campaign for you quite frankly. Not saying this in a negative way at all, I also like to rolePLAY sometimes, but it's just not that sort of campaign.