Those responses seemed pretty reasonable. Positive reinforcement via attack roll bonuses is a good idea, and I have considered the whole minion thing too.
The problem with minions vs standard monsters is this: you either get monsters that die in one shot, to the weakest attacks the party has, or monsters that take four or five normal attacks to kill. With no AOEs around, they are balanced, except minions can create more obstacles than a standard monster. Once a monster is identified as a minion, it can be almost literally pushed over and be killed.
Using a ton of minions means that AOE powers that are weak or balanced for combat vs standard monsters become overpowered vs standard combats. This is because of the four minions = one standard monster conversion; it's like aoe is hitting the same standard monster four times (or more, in the case of weak AOEs like dragonborn breath). AOEs are similarly less powerful when used against elites and solos compared to how they work against standard monsters. Coincidentally, elites and solos tend to make combats drag out longer just by being there, so they would be used less under this encounter design philosophy, making AOEs even better to use. Assuming that the classes were more or less on even footing to begin with, this means that a sorcerer would be automatically better than a rogue, for instance. I don't like this outcome.
The biggest problem with just reducing all HP values is a little bit more subtle, and one of the posters over there almost had it. He said that the issue was burst damage, but that's not quite all there is to it. The issue with burst damage is that monsters and PCs in 4e are balanced so that monsters almost always have access to their full HP, while PCs only have access to a small portion of it. The PCs then get access to the rest of their HP through powers and items that let healing surges be spent. By halving the length of combats, you effectively double the value of each individual action. The monsters "heal" automatically, but PCs will have to spend twice as much of their action value on healing as usual to stay up. And with the lower HP values, PCs will hit 0 hp more often, and have to spend more actions standing up and recovering from being "killed". To top it off, monsters will get something like 1/2 an extra attack on average because PCs will take slightly longer to kill them (ie a monster that took 5 attacks to kill will now take 3, but the actual value of those 3 actions is 6 actions from the old setup). All of these add up to favoring monsters over PCs.
There are some things that favor PCs, however. In a 10 round fight, a PC usually gets to use about 4 encounter powers and one daily power, then 5 or so at-wills. In a 5-round fight, the PC need not resort to at-wills, meaning that the PC's damage is increased dramatically if he lives long enough to get all of the attacks off. PCs also tend to use more action points than monsters, and action points are twice as good in the new system.
These things might balance out, but they make the first few rounds of combat much more important for PC survival then they are already (and they are pretty important). To smooth this out, it might be good to boost healing: eg. make all minor action heals into free actions, all standard action heals into minor actions, give everyone quickdraw, let second wind be used while unconscious, remove the one-per-round cap on using leader healing powers, etc. With the boosted healing, then there would need to be a nerf to reduce the impact of encounter and daily powers, such as capping it to 2 encounter powers and 1 daily power per encounter, or make such powers take twice as long to recharge (ie two encounters or two extended rests).
