Just interesting to note that 3 of those 5 can be combined for backstabbing with a double-enchanted Daedric dagger.

With a high sneak it's possible to regularly use the x15 modifier, I only use it if I happen to come up behind somebody, I rarely maneuver myself specifically to use it. Personally I've found the "bullet time" with the bow the most useful, makes it easier to take down groups of enemies while still in sneak mode.

of all the perks i've looked at so far, i think eagle eye has the most significant and immediately visible effect with the dual-weild spell perks coming in 2nd place

Double summons (Twin Souls) and 30% spell absorption (Atronach) really stood out to me while i played my pure mage.

Yeah, if the question is simply "what is the most powerful perk", this is easily it. Nothing else is even close -- you can outdo any other perk *tree* with this one perk if you abuse it.

For my play style I love the Zoom and 50% slow on bows. I also love the speech tree with Investor, Fence, and Merchant. The duel wielding perks are nice and I get around the no blocking with using two weapons with health steal