[ScruffMacBuff]

I solo pretty effectively at 56 in KC, it can be done at 53 with the right items. Key items include:

Silken Whip of Ensnaring
Polished Obsidian Great Axe

That's it. Now if you want to make it even more efficient you can add these nice optional items.

Fungi/Ceremonial Iksar Chestplate - Anything helps
Blood Fire for extra DoT damage
Runed Blade for sweet Rune 3 proc or Blood Points to heal back some health.

Pull a sentry to the exit and use the whip and blood fire until snare procs, if I get the boil blood proc then that's a bonus. Not necessary. As soon as it's snared you quickly swap to the great axe for a fear proc. Now once it's feared and running I switch to the Runed blade and hope for a proc so when fear breaks I don't take unneeded damage. Let it chase you back to the exit and fear it again. Sometimes I'm able to kill stuff in one fear, other times it takes a couple. Guardians and skeletons have more HP than the sentries so it will take a couple for them. I wouldn't take on a guardian unless you have evasive available to use.

I've had strings of luck where I can kill 3 or 4 in a row without stopping and end at about 50% hp which makes the following down time worth it. 4 or 5 kills is 1% exp for me right now.