First of all, I've tried damn near every Stalker build imaginable. Strength based Stalkers used to be effective until the addition of a one hand bow. There are no effective strength based Stalker builds anymore because the benefits of the bow greatly outweigh any strength based build benefits. Shield Chain works off of your attack and card benefits. Dex + Soaring bird has a much higher attack bonus than the Stalker dagger + Strength. Add in the fact that the bow gives more damage to demi humans, 20% more hp 15% reductions, why would anyone go strength?
The suggestion topic you mentioned about shield chain was about boosting the damage bonus given by Friggs. No suggestion to make shield chain elemental has ever been accepted and I'm fairly sure it will stay neutral for ever. If you wear a GR armor and Usakoring + fshield then Shield Chain will do around 2k per hit tops. This is no way comparable to the LK's ability to spam 4-7k per hit elemental damage. Sure, Stalkers can strip... but fcp tickets are easily available and almost everyone has an alt account or a friend to fcp them. When fcp brings your spiral damage to 2k per hit then we can maybe make a direct comparison to the two skills.
The Intimidate skill you're mentioning is not effective on this server at all. On this server it's called "Snatch". What does anyone do the moment you Snatch them and they get teleported? They @warp right back to where they were. The skill is at best an annoyance in pvp, not an effective way to combat an enemy. Furthermore, you can't snatch people in WoE, GvG, PvP arenas. Close Confine is also very ineffective on this server because the thief branch can backslide out of it, Champs can snap... and any class with a knock back skill (Jupitel Thunder, Smite, Bowling bash, Magnum Break) can break Close Confine.
My point in all of this is that sure a Stalker can stun-lock you with Shield Chain but overall it is not comparable to the LK's ability to stun-lock and kill because LK's can knock you out of pnuema and their stun-lock skill is elemental with a high damage output.
Now, on to Acid Demonstration:
You don't even need FCP to block this skill. RSX/GR + 2X Rays + usakoring fshield and Acid Demonstration will never even reach 1k damage per hit. Creators bolt skills are also limited as most of them are using a weapon that gives them the level 3 bolt. They are not an effective way of killing people and are at best an annoyance. Their damage output is in no way comparable to a LK spitting out 4-7k per hit spirals and capable of 22k x2 each hit with bowling bash.
I don't believe I ever mentioned anything about cloaking cards... that's you're choice.
I think you're focused too much on what classes were in the past (mentioning 2-2 and how things were before Charge Attack was implemented). You need to let go of that and look at how to keep balance now.
As for Mages: The Prof weapon needed Stave crasher. It's a fair and necessary attribute in order to give Professors some hope in pvp. When your entire offense is blocked by 1 card + fcp then you have the right to compare your class to the Mages... until then I don't see any necessary comparison nor any similar buff necessary for LK's.
You consider the fact that BB knocks people back a disadvantage. I would argue that it's more of an advantage overall. You get to push people out of pnuema and my favorite aspect of it is that you can knock those pesky Sonic Blow Assassins off of you and get down to spamming Spiral.
You don't need to wear maya purple + f.soldier. If someone is using puppetring and cloaking then use box of sunlight + f.soldier. You'll still have 3 card slots open for kiels making your spamming ability pretty hefty.
LK's can knock people out of cloaking pretty easily. Is slapping on a horong card that difficult? And you can also Magnum Break, which is much easier than using sightless mind on a Stalker, or Unchained Serenade on a Clown. The Stalker must be in Hide to use the skill (which greatly lowers movement speed) and the Clown goes into a song stance when using US so they can't start spamming Vulcan for a second. LK's can just run up, Magnum, spam spiral all very quickly.
There's no argument from me that LK's are OP. They aren't. They're balanced and fine as they are. They don't need further buffing or any sort of nerfing either. An sp boost would only give them the ability to hoard tons of yggs while having a huge HP modifier to tank.