Hey there, Toots. Just wanted to jump in with my 3 cents

I'm not sure if you're aware but the rest in between sets is designed to bring about specific results. Longer rests allow muscles to recover more, allowing you to lift heavier weights. This also yeilds more muscle growth due to more muscle tearing. Shorter rests are geared toward fat burning and keeping your heart rate elevated - they are more aerobic. Waiting a shorter time between sets doesn't mean you don't feel the 'burn', however the burn isn't quite the same as when you allow your muscle to rest and then lift heavy. What you feel after a short rest is more lactic acid buildup, and not actual failure/fatigue.

I understand the desire to do more for specific areas, but keep in mind that the compound exercises like chest presses and wide grip pulldowns work many muscle groups, including your core muscles. Many times after a focussed chest and bicep workout I have felt sore along my triceps and lats - it all gets worked when you do the compound exercises.

Heres to hurtin in the morning
-Nat

p.s. Just a thought - do you have heavier weights than those available to you? If you can flye 12 lbs you can chest press about 2x that much(one is compound, one is isolated) This could be why you dont feel like you're working out as hard as you should be - you aren't! (we women tend to underestimate how strong we really are)