Get that first pickpocket perk early on. That 20% boost, especially early game, will help tremendously.
Probably take that last perk (Bull's Eye) out and put it in the second Steady Hand. I heard Bull's Eye is kinda buggy, like they'll paralyze and fall at the beginning of a killcam and then your arrow will miss.
Its still worth it since it stacks with a paralyze bow.
As for the general build, I roll with a Dark Elf Vampire Assassin. I'm unbelievably OP and I'm unfair without stacking.
This is how I got there:
http://ca.ign.com/builds/the-elder-scrolls-5-skyrim?d=0000000000000000001011111111110100010110000000000000000000000000000000000000000000510011111111111000000000000000000000000000000000000000051111231150000000011111151111111011111001111
Equipment:
Dragonplate everything (substitute with your enchantable light armor of choice for non-Dawnguard play) +1 necklace and 1 ring with these enchants
resist frost, fire, shock, magic
fortify health, stamina, magicka, sneak, archery
Dragonbone Bow with these ehcnants (I enchant a set of blacksmithing armor and use potions to create a 700 damage bow, you can stack if you want but I'll tell you right now, anymore then 700 damage gets silly)
Fiery Soul Trap, Paralyze
Then what I do for combat is this:
Sneak (if you did it right you will be undetectable, Ive had enemies brush up against me and they haven't detected me), cast Mayhem, summon 2 Dremora Lords, start shooting your arrows.
When you see a dragon don't use mayhem, instead use your marked for death shout and dragonrend and lol as your dremora lords+your bow eat it for breakfast. If its a tough dragon then bide your time and keep casting marked for death (its effect stacks so it'll have -armor and take stupid amounts of damage per hit).