I just recently got back into COH so I cant judge your build with any authority. Actually, I have a lv 27 Kin/EA stalker and I will be watching this thread to see if any wisdom pops up in here that can help me as well. Sadly, I have to say that I have put my Kin/EA stalker on the shelf in favor of RAD/EA. The reason I put Kin down is because my experience largely mirrors this post i saw in this redit post.
"You'll have your best single target attacks by 6th level. Yup, 6th. Quick Strike, Body Blow, Smashing Blow, and Assassin's Strike are your core attacks. At 18th level you get your AoE and everything after that is a gimmick. Focused Burst is a ranged attack which is cool and all, but eventually it pales in comparison to the first 4 attacks.
Concentrated Strike is a total gimmick. Absolutely toy with it if you like, but what it looks like on paper is not reflected very well in reality. For starters, despite having higher DPA on paper, the first 4 attacks will eventually out perform it. Despite the Build-Up refresh mechanic, the added up-time doesn't create a DPS increase.
My KM/SR has all the attacks. I use them all from time to time, but if I am playing seriously and want to drop a hard target I don't touch the gimmick powers.
Scrappers are in the same boat. You won't use the gimmick powers if you're being serious with the single target.
Sounds bad, but on the plus side it is a set where it matures very early. With high recharge it is a rapid chain of attacks."
As a stalker I was always in melee range so I couldn't find any practical value in actually having ranged attacks. the fact that concentrated strike cant crit undermines kins burst damage and the buildup mechanic is undermined by assassins mark. On a side note, I am also disappointed that kin melee lacks the siphon/buff/debuff of other kin sets.
I hope things work out for you with kin. And if they do, please come post about it. Kin has some cool animations and I want to like it. I just found the low tier powers to be competent but shallow/repetitive and the high tier powers to be cool on paper but impractical in practice.