Inspired by this thread a few weeks ago, I came up with an idea yesterday at work. Here's my thoughts, transcribed from my hasty scribblings on a piece of paper:
Twin Strike - Ranger Attack 1
At-Will * Martial, Weapon
Standard Action
Melee or Ranged weapon
Requirement: You must be wielding two melee weapons or a ranged weapon.
Target: One or two creatures
Attack: Strength vs. AC (melee; main weapon and off-hand weapon) or Dexterity vs. AC (ranged), one attack per target.
Hit: 1[W] damage per attack. If you target a single creature, 1[W] + Strength modifier (melee) or 1[W] + Dexterity modifier (ranged).
Increase damage to 2[W] damage or 2[W] + ability modifier when targeting a single creature at 21st level.
A slightly modified Twin Strike, allowing a controller-ish aspect by spreading the damage output but not allowing for such incredible concentration as before. The wording is still a bit of a problem, but this should allow for mixing it up (deciding which weapon to attack with, potentially using a thrown weapon against one target while engaging another in melee etc.).
So far not so different from some of these suggestions. In fact, it seems weaker at first glance. That's because I've left out the key ingredient: Wisdom, the bastard tertiary ability score of all rangers. How could I make Wisdom a more suitable secondary score for all rangers, rather than a tertiary? I decided to begin with Twin Strike. What I originally went for was this:
Effect: The target takes damage equal to your Wisdom modifier.
I know, auto-damage is the devil. Yet this is a clean and effective way of securing the rangers damage capabilities without nerfing them all together. Strikers aren't meant to attack minions anyway, although this helps rangers (yet again) facilitate as the de facto "martial controller".
This seemed fine at first, but then I started getting into the real issues plaguing the ranger: the fighting styles. As it is, Two-weapon fighting style is generally considered better than any of the other options, regardless of build (unless you're a beast-master, which is more of a RP attraction really, in comparison). So how could these options become more balanced? Well, my initial reaction was that the styles were rather ugly remnants of 3.5 due to the free feats they gave (Toughness > Defensive Mobility). As the game has evolved, new ways of granting classes defensive boosts when suffering from MAD and more balanced build mechanisms have emerged. I came up with these changes to the fighting styles:
Archer Fighting Style
Because of your focus on ranged attacks, you gain the benefits of your Prime Shot class feature against your quarry on ranged attacks, even if any of your allies are nearer to your quarry than you are. In addition, you can add your Wisdom modifier to all defenses against opportunity attacks.
Two-Blade Fighting Style
Because of your focus on two-weapon melee attacks, you can wield a one-handed weapon in your off hand as if it were an off-hand weapon. (Make sure to designate on your character sheet which weapon is main and which is off-hand.) In addition while you are not wearing heavy armor, you can use your Wisdom modifier in place of your Dexterity or Intelligence modifier to determine your AC.
Now, this might actually be more unbalancing than balancing, but maybe someone better with numbers could check this out for me. I considered removing the long range penalties for ranged weapons for the Archer ranger, but that seemed less likely to occur regularly and felt a bit like overkill (scenario: quarry target, run away and gain prime shot 30 squares away :/).
To finish things off, I also created a subset of style-specific tweaks to Twin Strike as an alternative to the Wis-mod auto-damage I first came up with (added indented under the Hit line):
Two-Blade Fighting Style: If you targeted a single creature, you deal additional damage equal to your Wisdom modifier.
Archer Fighting Style: If you targeted a single creature, you can slide the target a number of squares equal to your Wisdom modifier.
Beast Mastery: If you targeted a single creature and miss, your beast companion can make a melee basic attack against the target as a free action.
This solidifies the two-weapon build as the heavy striker, the archery build as controller and the beastmaster gets some love for versatility. Now that I think about it, one might as well combine both of my options for Twin Strike. But as I said before, someone with better math skills than me should probably take a look at this.
Anyway, that's my two cents.