I currently have a level 13 Ranger and here's what he'll look like at level 16. We used rolled stats, but I converted it to point buy. We also are only allowed to use the first 3 core books and the Adventurer's Vault, so you might have more options with other books.
His focus is on doing damage, since once we hit paragon we added two players and both are defenders. He's only been bloodied once in Paragon.
I changed his gear to level 12 treasure as well so he's compatible with your game.
His basic tactics are to get in, hit with the close bursts, then skirt around the edges taking out cold-vulnerable damaged foes. Be sure he ends up next to two enemies whenever possible so he can do his automatic 10 damage to one, 5 to a second.
He has a multitude of encounter powers that allow him to shift out of the fray once he's out of burst powers and stay out of the head of it, using his boots to teleport out if things get too hot. His defenses are also pretty solid (excepting his puny will) so he can survive in melee for a while.
Use Rain of Steel if it looks like a tough fight with lots of enemies then stay in the thick of it as long as you can. The fighter multiclass feat encounter (+1 to hit and mark) is a good one to use on Disruptive Strike(especially if they're attacking someone else, extra -2 to hit!) or Cascade of Blows.
In practice, he's only been dropped to 0 once in 13 levels. He rarely gets bloodied and, especially once he gets enemies cold-vulnerable, can do huge amounts of damage with pretty decent amounts even if he misses (does 20 damage to a single target + 5 to a second target even if he misses).
This is by no means the only way to build a ranger, especially with martial powers out, but it's the way I'm going with my character.
====== Created Using Wizards of the Coast D&DI Character Builder======
Logan Banner, level 16
Elf, Ranger, Stormwarden
Build: Two-Blade Ranger
Fighting Style: Two-Blade Fighting Style
Student of the Sword: Student of One-Handed Weapons
FINAL ABILITY SCORES
Str 21, Con 11, Dex 21, Int 11, Wis 16, Cha 9.
Starting Ability Scores
Str 17, Con 10, Dex 15, Int 10, Wis 13, Cha 8.
AC: 29 Fort: 26 Reflex: 27 Will: 23
HP: 108 Surges: 6 Surge Value: 27
TRAINED SKILLS
Nature, Perception, Stealth, Acrobatics, Athletics, Intimidate.
FEATS
1: Quick Draw (Key since you have two weapons to draw and sometimes might need to switch to your bow in a hurry).
2: Weapon Focus (Heavy Blade)
4: Two-Weapon Fighting
6: Student of the Sword
8: Wintertouched (CA vs cold vuln FTW)
10: Adept Power (For Rain of Steel - works great with the Stormwarden auto-damage shtick - I've done 50+ damage in a round when it was active and that with missing on every attack)
11: Lasting Frost (Cold vuln FTW)
12: Scimitar Dance (5 damage on miss FTW)
14: Lethal Hunter (d8 quarry)
16: Blood Thirst (+2 damage vs bloodied. If you want more defense, get Two-weapon Defense instead)
POWERS
1, At-Will: Hit and Run
1, At-Will: Twin Strike (Bread-and-butter)
1, Encounter: Dire Wolverine Strike
1, Daily: Jaws of the Wolf
2, Utility: Yield Ground (When hit, shift 3 and +2 defenses)
3, Encounter: Disruptive Strike (Interrupt enemy attack, they take -5 to hit)
5, Daily: Two-Wolf Pounce (retrained to Rain of Steel at Adept Power)
6, Utility: Weave Through the Fray (Enemy moves close, shift 3)
7, Encounter: Sweeping Whirlwind (burst and push)
9, Daily: Attacks on the Run (Big 1-2 target damage + movement)
10, Utility: Expeditious Stride (Minor action +move)
13, Encounter: Armor Splinter (replaces Dire Wolverine Strike) (Pre-blade cascade debuff)
15, Daily: Blade Cascade (replaces Jaws of the Wolf) (The big cahuna)
16, Utility: Evade the Blow (Daily interrupt and shift when hit)
ITEMS
Magic Longbow +1 (because you need to make ranged attacks sometimes)
Frost Scimitar +2, Frost Scimitar +3 (cold damage FTW)
Amulet of False Life +2 (when bloodied, get healing surge temp hp as minor)
Magic Earthhide Armor +3 (basic with a fort buff)
Feystep Lacings (paragon tier) (reflex boost and emergency teleports)
Iron Armbands of Power (heroic tier) (+2 damage to all melee attacks!)
====== Created Using Wizards of the Coast D&DI Character Builder======