Halving HP of everything is a somewhat good solution but it just solves one thing (high hp) and leaves the other two issues (low damage, low attack) unanswered. That's why I insist so much on my rule; it answers all 3 issues.
Another "hidden" advantage of my rule is that it allows for a greater variety of combat encounters. The ability to add X attack bonus (X=your lvl) for an X hp cost can allow low level creatures to strike beings of a much higher level with something other than a natural 20. Here are some encounter examples that are a big NO right now and can become a big YES with my rule:
1) A dozen of low-level standard monsters that their attack is too low to threaten the party. (normally, the party will win with ease but, with my rule, the monsters just have to trade their max hp possible for max attack in order to have a fair chance to win this fight)
2) High-level minions that their defenses are too high to be reached by the party. (normally, the party has no chance but, with my rule, they just have to trade their max hp possible for max attack in order to just hit the minions)