Frenzy is good for prolong fights (Boss fights) because you can maintain your stacks. Since you are going Barb2, you will have a max of L5 Frenzy = +15 damage x 10 stacks = +150 damage with 40s duration. Assuming you do 1 attack, it will take you 10s to full stack. Use skills with new buffed damage.
Frenzy is bad for fighting mutiple enemies. You lose half your stacks (only possible if you are barb3) if you strike another target. If you group a bunch of monsters and you autoattack the clumped group. you will lose basically all your stacks. Since you are Barb2, you will lose all your stacks if you strike another target
Frenzy tip, if you get full stacks you can use AoE spells and still retain the stacks, its only when you auto-attack a new target is when you lose half.
You say you want burst damage, but you have to consider that frenzy is good in certain situations