The greatest gift the Mesmer secondary gives to the Ranger is the skill Arcane Conundrum.
Give this build a try:
Marksmanship: 16 (12+3+1)
Expertise: 9 (8+1)
Wilderness Survival: 8 (7+1)
Illusion Magic: 8
Read the Wind
Penetrating Attack
Punishing Shot {E} or Poison Arrow {E}
Savage Shot
Distracting Shot
Arcane Conundrum
Troll Unguent
Rez Sig
Nice mix of damage and interrupts.
Arcane Conundrum allows you to easily interrupt things that are normally much more difficult to interrupt, specifically 1 second or less spells. And you still get decent damage output with Read the Wind, Penetrating Attack (about every other attack), and Punishing Shot/Poison Arrow.
EDIT: On a side note, if you want to be a good interrupter, leave Barrage at home. Simply put, you need Read the Wind to be a fully effective interrupter, and Barrage unfortunatley does not work with Preps. Besides, the Read the Wind, Penetrating Attack, Punishing Shot/Poison Arrow combo I described above out-damages the hell out of Barrage in terms of single-target damage. Save the AOE stuff for the fire Elementalists and just concentrate on your interrupts (while dealing high single-target damage between interrupts, of course).
Barrage is wildly overrated BTW.