New grinding areas (I/L)?

Umm...If I do 3 amp 1st, I'll receive a 111% damage boost at lv71 with lv3 amp, and then start maxing out IS, basically I'm maxing IS 1 lv later than usual, but receives a 111% damage boost, is that not enough to compensate the lose?

Oh and I'm not gonna use IS after it's lv16 or more right?(or am I totally wrong about this? I have no idea) So 111% to lightning bolt would help abit.

Unfortunately, it's just an extra 11% damage. >_> And yeah, I didn't really use Ice Strike until it could hit two platforms at Windraiders (13?), but it's still nice to freeze them, and the sooner you have your level 28 Ice Strike the better off you'll be, as it makes things a hell of a lot easier on you, even if you're still training at Windraiders.