At 16th level:
Da Bleeder, Longtooth Shifter Beastmaster Ranger (multiclass spellscarred)/Ruthless Punisher
Str 22
Dex 11
Con 14
Int 11
Wis 22
Cha 10

Relevant Feats:
1 Multiclass: Spellscar
2 Cruel Cut Style (from Dragon 373 - Art of the Kill)
10 Daily Power Swap (Caging Strike -> Blurring Blade)
11 Bleeding Precision (add +5 ongoing untyped damage to all Ranger daily hits)

Relevant Powers:
Predator's Strike (at-will): Deals ongoing damage equal to Wisdom modifier instead of bonus damage equal to wisdom modifier. (Via Cruel Cut Style).
Spellscar 5 - Blurring Blade (stance; all encounter long, all enemies starting within 1 square take 11 ongoing fire and necrotic damage (save ends))
Ranger 5 - Lacerating Maul (16 ongoing damage on hit or miss)
Ranger 9 - Caging Strike (21 ongoing damage on hit), swapped for Blurring Blade (Spellscar 5)
Ranger 15 - Arterial Strike (ongoing 21 / aftereffect ongoing 16, reliable)
And later on:
Ranger 19 - Growling Assault (ongoing 21 on hit or miss, if target is immobilized)
Ruthless Punisher 20 - Bleed Away (up to ongoing damage 71 if the enemy doesn't want to be moved, but realistically, the enemy will allow itself to be pushed around to avoid taking that much damage)
Ranger 29 - Huntmaster's Bloodbath (ongoing 31 on hit / 21 on miss)

Relevant Items at level 16:
+3 Amulet of Aranea (16 ongoing poison and -2 to saves vs poison all encounter)
+3 Wounding Weapon or +4 Cunning Weapon (-3 to saves vs ongoing damage, and wounding can inflict 16 ongoing untyped damage on a hit as well)
Caustic Whetstone (8 ongoing acid damage with every melee hit)
Optional: +3 Snakefang Armor or Addergrease Armor (16 ongoing poison damage), use after Aranea damage has worn off.
Optional: Salve of Power to recover blurring blade.

Relevant PP Powers:
16th Level Ruthless Punisher: +Wisdom to all ongoing damage, and CA against humanoids taking ongoing damage, which could be all of them.
(It also deals +Wisdom to all melee attacks vs. Humanoids designated as quarry, which can be a nice damage boost.)