Anyway, at which aspd breakpoint do you guys think its ideal (sweet spot) to get without sacrificing too much other stat?
Unfortunately, that's not an easy question to answer.
As you said, as your attack speed goes up, your ability to freeze mobs also goes up, with the ability to at least keep single target mobs "stutter locked" at around the 2.74 break point.
As you decrease mobs abilities to do nasty things to you, your need for armor/vit/AR also goes down, in most cases.
I have roughly the same survivability now (see profile for stats) as I did when I had 40k vit, 1100 AR (with Energy/Prismatic), 5.5k armor and only 1.6 attacks per second.
But (and this is a rather big but), you become much more dependent on playing skillfully as you rapidly lose the ability to take even a single hit in the upper MP levels. You gotta keep an eye on your cool downs, etc. etc.
Unfortunately, in order to hit the high break points, you need to start using equipment (Shandlar has already posted about several of these items earlier) which are going to decrease some of your survivability stats.
It's up to you as to whether or not you want to lose survivability at the cost of reaching the next break point.
IMO, I'm having much more fun playing a "ragged edge of survival" build (my definition: killing stuff fast but always being one hit from death).
As your attack speed goes up, your ability to maintain your survival stats becomes much more constrained by the gear you have to choose, as well as your bank account.
Edit: I should mention that going over the 3.00 break point has a rather pronounced effect; your survivability goes up a lot more than what you might expect. LoH, CM, etc (all the nice things that happen with IAS) seem much more amplified than at the earlier break points). Switching over to the gear I have to use to hit that break point drops me down to only 24k(!) health, but my ability to survive goes way up. Unfortunately, I also lose a ton of dps, so I don't actually *play* at this break point, but it was fun to test and see the difference it makes).