Also, consider these potential weaknesses in your build: 1) you have poor OA ability, which isn't good for a defender 2) almost all of your powers are short-range attacks, with only a single at-will and encounter melee power at 11th level, which is also a sub-par choice for a defender, and switching between melee and ranged makes you vulnerable to OAs 3) you've burned almost all of your feats on multiclassing 4) you've chosen the sub-par paragon multi-classing over a paragon path (i.e. you're gving up the two 11th level path features and one 16th level path feature for the ability to swap out an at-will power) 5) Lay on Hands requires you to be adjacent to your allies, which is going against the ranged attacker role your build seems to be taking on.
I don't think those things end up ultimately being weaknesses(at least not compared to the strengths)
1) If they choose to ignore me, I ought to do around 1d8+11 at 1st level and the target is likely at -4 to hit due to Enfeebling Strike. I still get the opportunity attack, even if my odds aren't good. Slightly worse than the typical paladin, but...I don't think they're ignoring me.
2) My attack range is typical for a Warlock. Eyebite, Hellish Rebuke, Dire Radiance, Curse of the Black Frost, and Mire the Mind are all range of 10. At low levels, this can be Dire Radiance and then position myself in a place where it is impossible to move towards the party without also moving towards me. That can easily be 22 hp of damage in a round on average at 1st level.
3) Yes, but I'm also a high AC/Defense/hit point/14 healing surge character who does actual melee/close range damage. Which is to say, I want to open up with a ranged encounter and then move up rather than move up and melee encounter - this gives me flexibility. Mire the Mind is great for this as it will make the entire party invisible to the target, psychic lock the opponent, *and* let me move up to someone else while the strikers take 'em out the original target.
4) I don't think this ends up being that huge of a disadvantage in LFR - the characters that pick paragon paths are stuck with the powers they get from them. Given 1-3 years of power creep, I bet the Warlock powers I get from them will eventually be significantly better. Granted, the paragon paths are generally better, but it is hard to do what this guy is doing - being able to consistently smack people at range or in melee without sacrificing defenses or hit points. At higher levels, being able to mark and then attack flying creatures should be worth a lot.
A big hidden advantage for the build is that he's really only going to need one implement, his pact blade. He avoids paying up for 2 implements like most paladins have to do, by using those feats to minimize it.
5) Lay on Hands - the guy's a melee character primarily - his only real limitation here is that he's a 12 Wis Paladin.
----
I'm interested to see how it plays out myself.