Don't forget one advantage a Warlock has in utility that a Ranger cannot compete with. Wands. Capable of storing Encounter and Utility-Encounters of a Warlock(And Wizard) in a wand that can allow you use them Daily if you are holding the wand. Also, there don't seem to be any disadvantages to holding TWO wands, a weapon and a wand in the off hand, or a rod and a wand. You can only use one of them as a focus for any power.
Why would that be a notable advantage? At level 21, three rounds of using Infuriating Elusiveness in one encounter daily if you have the power and have decided to wield two wands containing that spell. Thats Turn invisible till the start of your next turn and teleport four squares as a Move Action. So you could easily Blast as a standard action, then turn invisible and teleport as a minor action till your next turn three times in a row in combat. Or it could be instead three turns of hitting an opponent with Strand of Fate, the one that gives either Vulnerability 10, or if Star Pact Vulnerability 10+IntMod. Expensive, given the cost of Wands as a Magic Weapon, but doable.
How about Stealth? With a Warlock's Shadow Walk. Move 3 or more steps and you can make back to back Stealth checks due to the Concealment that Shadow Walk gives. While other classes would need to use natural cover or a power, a Warlock trained in Stealth could walk right past some rather Perception lacking but alert Grunts at high noon and never be noticed, though at a -5 Stealth check due to movement. You could even fight by simply blasting, moving, then making a stealth check. Especially useful since Stealth fails if the opposing is not either distracted or has line-of-sight. At Paragon levels, take the Secret Stride feat and ignore the -5 Stealth check part.
Warlock's Curse also has an advantage. While the Hunter's Quarry can only target enemy at a time, Warlock's Curse doesn't have the same One Enemy only clause. Especially nice as there is a Magic Rod Implement for Warlocks which allows you to spread the curse to every enemy in a Burst 5 when an enemy dies under your curse, rather then use your Pact ability. Its really nice as the minor action will always be a Warlock's Curse, unless there is a sustain or another action needed.
Then there is the vs Def. Clerics, Fighters, Paladins, Warlords, and Wizards have powers that can boost AC quite commonly, making them and/or their allies harder to hit. Heavy Armors also give equal or more defense then the Fort/Ref/Will defenses get from their respecitve stats, while even Light armor gives at least +2 on top of their Int or Dex modifier. Though the Warlock will end up facing against more common resistances, there are still vulnerabilities to take advantage of as well.
Though, even with all of that, there is still the option of Multiclassing. Warlock multi-classing into Ranger and spending a feat on getting a bow proficiency. Just grab the most damaging Ranger Daily and Encounter while going Fey-pact Warlock for movement and other fun utensils....shoot new idea.
Feynger The Arrow's Shadow-Warlock multiclassing into Ranger with focuses on Cha and Dex for abilities. Train in Stealth and get the Skill Focus for Stealth as well the 3 Multiclass feats on top of Warrior of the Wild also train in the Longbow unless you are the Elf race. For the Pact, go for the Fey for Misty Step for each kill and Eyebite in case for the need for an at-will temporary invis against someone who beats your Stealth check. Grab the most powerful Encounter and Daily from Ranger skills, and at 11th, trade the Eldritch Blast for the Twin Strike at-will. For Utility, I wouldn't worry about it unless its up to personal taste. At 20th, trade in the Paragon Daily for the 19th Daily from Ranger Two-in-One shot. For fighting? Keep moving 3+ squares to keep concealment and stealth while attacking with the bow at range, using encounter abilities to spike when you allow the enemy to draw in close.
Bwahaha. =} Gotta see if I can actually put together such a build.
I admit, the Ranger has the better one turn damaging move and range over Warlocks. No comment on any other part of the class which is harder to take.