I figured out a Maxed Skill Perk based on everyone here's comment. I picked up all the matching ideas from you guys and figured out a Assassin Perk. Maxed out all I could and found necessary. The only two skills I poorly upgraded was Light Armor and Archery.
Remember: As an Archer, I'll not chose to directly combat my opponents using a bow. I'll use the bow strictly to sneak and kill too far away enemies or other archers. It's not my main weapon.
And it makes itself obvious why I did chose only 5/5 light armor perks.

Again, what's the point with alchemy anyway.. it's so boring yet so necessary.
First let me say that I find smithing and enchanting ruins the game for me because I no longer need to find better items I just make some godly weapons/enchants and faceroll the world. So in order to keep some challenge on master difficulty I keep all of my characters without crafting with the exception of alchemy. By not including them I have to deal with picking the right tools to do the job. 100 smithing/enchanting on any build with or without perks provides to much reasonable benefit if your looking for a challenge.
With all that said my ideal assassin setup was this http://skyrimcalculator.com/#22859. Granted I use a bow heavily to avoid direct combat and I have limited armor perks because I'm not looking to fight anything straight up. If I get into a tight spot I just drink an invis potion and re-hide. Or shoot a frenzy arrow into a crowd of enemies, or stuff a paralysis potion into someones pocket.
My choices were made for the following reasons...
Archery - My mainstay misdirection damage from a far tool. Stagger lets you plink down almost any enemy and doing it faster is doing it better, which is why I went up as high as Quickshot. I don't particularly like the slow down perk, I don't find it adds much value to my play-style, but others may want it. Archery IMO is valuable for a few targets specifically, one that comes to mind immediately are Dragon Priests.
One-Handed - I only took enough to get the specific power-attacks because they all receive the sneak bonus and when approaching heavy hitters this will ensure that they die. (Remember no 50+ damage daggers in my pockets). You can of course work around this tree entirely by one-hand power attacking and following up with another strike to finish off the target. Or sneak attack with arrows from afar until the target is within assassination health. My preferred weapons are a dagger of stunning and mehrunes razor.
Light Armor - Just enough for Unhindered. Again I'm an assassin not a street fighter, I have no need nor any desire to fight anything toe-to-toe. I've actually made an assassin before who wore nothing but clothing and he was insanely powerful. Armor is overrated, though it does look cool.
Sneak - Obviously the assassins trademark stealth. Fill it up, all are useful and good tools in the toolbox.
Pickpocket - Marginally unnecessary, but fun skill-set that can be useful and brings some laughs. The only perk I would rate as important is Extra Pockets, but even that can be dropped for other more useful perks in different trees. This is probably one of the most unused trees for min/maxers and there's no mystery why. However it adds a layer of fun to my gameplay that I enjoy. Shoving frenzy/paralysis potions into peoples pockets is just fun for the whole family. Not to mention pinching some cool items early on is also fun. Steal Cicero's Ebony Dagger early, or the Blade of Woe, etc. You can drop the whole tree and shave off 11 levels if you want.
Alchemy - Last but definitely not least a valuable tool in any assassins toolbox. From resist potions, healing potions, fortify potions, over to paralysis, frenzy, invisibility all in one. The concentrated poisons perk has limited value which is why I stopped there. Short of using a paralyzing potion on two targets coming at you, this perk would offer limited benefit as your potions at this point will last a good duration removing the need to keep going. Not to mention ingredients are readily available so you simply make more potions.
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With all of that said, I'll say there has never been an instance where I wasn't able to re-stealth and go back at killing a large pack of targets without using magic. Illusion requires heavy perking to be effective and certain dungeons will leave you without a tool to use unless you take the top tier perks (daedra, automatons, and undead). This is of course with the exception of Invisibility which is readily available in potion form even as a budding alchemist, no perks required. You could in fact skip all of the alchemy perks and still make paralysis and invisibility potions and you would still be very effective.
You could go all Illusion, Conjuration and Sneak and butcher the world to; which by the way is immensely fun. I stay stick in whatever tickles your fancy, but for Illusion to reach its top potential, you'll need heavy magicka investments, Illusion casting cost reductions and heavy perks.