dark, its really funny, fearsome stare + tar patch + flamethrower + Full auto = mwahahahaha. Mob falls over and u dont even need to use darkest night, the dark servant heals you and immobs/holds the mobs so you can toast them with ignite
**Acceptable "support" responses**
Its your fault
Its your computers fault
Its your ISPs fault
I'd think Kin has better synergy with AR, being able to fire off FSed Full Autos.
Also, Dark doesn't have -def. Tar Patch is -res, maybe that's what you were thinking about? The fear won't work well with Ignite, because mobs get a chance to move or otherwise react to you in some way once they're hit. It's still a great power, and I love the set overall, I just don't know that I'm seeing the synergy. Full Auto over Tar Patch could be kinda nice, but it's not going to be FS + Full Auto, and I've heard Buckshot is pretty weak.
It's true enough that a /Dark will be more soloable than a /Kin, though. You certainly get more to stop incoming damage. If you really can't choose between them based on how much you think you'd enjoy them, then it probably comes down to whether better synergy between sets, or the ability to solo safely, is more important to you. /Kin certainly can solo, anyway, it just tends to be a little more hectic and filled with more debt. 
But doesn't /dark have hold aswell, that'd work with ignite.
NOTHING Is the same as fulcrum shifted attack, but since I tend to solo alot, I reckoned that /dark would be safer than /kin.
I also get confused with -Def and -Res, but I was thinkint tar patch would work because I won't get much out of fulcrum shift while soloing (cept mayhem missions). Plus with it I can keep my distance while laying cones to res debuffed foes.
Protagonist, don't you already have an AR/Kin at level 50? Are you seriously considering playing another? I'd go with Dark if I was you, Tar Patch is great for slowing down the enemies to make the best use of your cones and Ignite, not to mention all of Darks other excellent powers
I do. On Defiant, so I was thinking of making one to union, because it was the only cov combo I found appealing (plus I don't have any good toons that I enjoy playing atm), but now I'm thinkig that what if /dark is more solo friendly.
Don't get me wrong, I do team when asked, but 70% of the time I solo.
I'd go /Dark. You might have some End issues (or at least more than kinetics) and less recharge goodness, but you can totally control a mob to death. I don't need to tell you how godly is the Tar Patch + FStare + AoEs combo.. it's just too good. Moreover, you can end up with 2 pets. What's not to love? 
@False Fiction - Virtue / Defiant
Current projects - [Glaciologist - Ill/Cold Troller] [Cloudshaper - Storm/Dark Def] [Harald Wartooth - Elec/Psi Domi]
With any other primary set I would take /kin anytime, but having tried the combination for some levels I have to say that ARs activation/redraw times have an adversary effect on kinetic goodness. Additionally, Full Auto is not too good with Fulcrum Shift and Siphon Speed. Yes, it hits really hard and recharges very fast, but running in for FS, then running (or super-hovering) back to get the whole spawn into the cone just doesn´t feel right.
So, I would recommend something else and /dark would actually be quite a good choice since you would have some nice powers to set the enemies up for nice deadly cones.
If it has eyes, you can blind it, if it has blood, you can make it bleed, if it has a mouth, you can make it scream.
The redraw time hardly gets in the way with AR/kin, I could easily siphon a mob, run in, get FS and possibly heal, set back a little and fire flamethrower and full auto and do the same trick on nearly every mob. 
Edit:
Ok I rolled Gaspard on Onion and so far the dark seems promising, especially tar patch which you get early in the game. I could dive into a mob of +1 skulls, beat them all and survive with it.
Dark for sure. It does have a hold yes but it's not an essential. Slot tar patch with a couple of slows and you can use ignight perfectly well. On my dark/dark i like to lay tarpatch on a corner and pull lots of mobs with DN, then use my cone attacks to whittle them down. Should imaging this would work even better with AR.
Kitty's top tip for the day: slot 2 acc debuffs in FS, you really notice the difference.
I miss him in the weeping of the rain;
I want him at the shrinking of the tide;
The old snows melt from every mountain-side,
And last year's leaves are smoke in every lane;
But last year's bitter loving must remain
~Edna St. Vincent Millay
Yeah, the hold could work for that. Once you have Fluffy, his immob might help, too. And /Dark certainly will be safer solo - as I said just matters what your priorities are.
Personally, making a /Dark, I wouldn't go with AR because I don't really see a huge synergy there (although obviously, to some extent, that's opinion) - if I want AoEs/cones over Tar Patch, I'd think Fire/Dark, really. But if your main choice is that you want to play AR, and then you want a secondary that will help you solo that AR, then /Dark makes a lot of sense. Especially if you already have an AR/Kin - might as well try something new, right?
HowdyHoHo.
I'm going to create a new alt, AR corruptor on a different server. I'm just unsure about the secondary because I have two options and they both sound good, either dark or kinetics.
Kinetics had those lovely self buffs and fulcrum shift that were awesome combined with the cones, not to mention endless end, SJ power and powerful heal. Plus I already know the set.
But then I was thinking, what if I went for dark, it seems more solo-oriented and I'd like that. Dark has the -acc so that enemies will be shooting/hitting air while trying to hit me, long distant heal with -acc ,aoe -def, pet that also does -acc plus hold and fear (could apply ignite earlier in the game).
How great is the aoe -def when you think about the cones of AR?
Sucha hard choice.