Just letting you know, you broke the first rule of hero sugguestions: Format.
http://forum.valor-zeal.org/viewtopic.php?f=32&t=37
Also, I think (may be wrong, but...) you broke the first rule of DoE as well, the only slowing effects in the game are Maim and Cripple, so your ult needs a bit of reworking.
As to the hero itself...
Time Swing: Interesting... actually took a couple read throughs to figure out what you meant, but that may just be me. Honestly, while it is interesting, I think the fact that it only comes into effect if the enemy falls below some health (or ends two ticks) is limiting, not only in the stacking side of things, but also in the fact that there's nothing creative you can do with this skill, it is, in essence, just a point, click, forget spell that you have to remember to fire off every 15 seconds (or whatever the cooldown is). If the skill were somehow more interactive, with more play with the battlefield as a whole and the other heroes, I think it would be more fun. Really, the best example of the workable form of this would be from AotZ's time based hero (And for the 2nd or 3rd time today, I'm blanking on the names, but anyways...) which has a skill that targets an aoe, and after a few seconds, does damage to it. It's simple, but effective. If you can work something like that into the hero, that would be nice. Something that's avoidable if their timing is better than yours, but if you've got the edge, you'll be putting the hurt on them.
Example Idea:
Time Bomb: Active Delayed AoE. Deals X damage and extends all conditions currently on damaged units by Y. Damage and extension are done Y seconds after the initial cast. If time bomb is cast again before Y seconds have passed, the first bomb will not activate until Y seconds pass from the second cast. Max number of Time Bombs active at once is Z. X and Z increase with level.
Something like that... anyways...
Two Ticks: Ok, well, shit... with the idea I just mentioned, this doesn't work, but that's not the issue at hand (thankfully). So what we're talking here is in essence a specialized version of the spell that makes units ethreal... um... ok? I mean, it's interesting, I'll give it that, but there's no magic to it... where's the life, the creativity? All you're doing is holding something in place so that you can... poke at it. No, this hero (at least the poem-y thing) has too much life to have a spell that causes you and your opponent to just take turns standing there. If you want an ability to be fun with something like this, why not make it so you have a skill that (hopefully without channeling) tosses a unit "forward in time" a few seconds (heh, for fun, make it two seconds, you know... two ticks?, and just have the cooldown decrease with level to the point where you can have fun with it, really disrupting the flow of other heroes by making them disappear randomly during battle?). It's an idea, at least.
Dark Claws: I've been there, hell, we've all been there, when there just isn't another skill you can think of to round the hero out. It happens. However, the third skill is kinda the breaking point for heroes. Either everything works or you're left with almost a hero, something that works in a loose sense, but never really gets a life to it. If you're looking for something that gives you good condition interaction and keeps the theme of the hero, why not look to the past? Time control is as much about the present and future as it is the past, so make use of it. Here's an idea:
Through the Never (passive):
Every time Slift uses a skill or kills a unit(?), a nodule in the timeflow is created. Whenever he takes a total of X% damage, he is returned to the last nodule with that health restored. Can have a max of Y nodules. Also, the nodules are visible as a small dark cloud/rift in spacetime.
Needs work, but at least it's got something to it. (actually, I just realized I've kinda neutered this guy, as right now he has one attacking spell... meh, such things can be dealt with later, such as making Through the Never deal X% damage to the unit that triggers it or something...) Anyways...
Strike of Infinity: I think i already mentioned the main problem with this one, the lack of stackable slows in DoE. I don't quite see much in the way of changing this... However, the skill itself shows promise. It just needs to be properly brought to DoE, so let's see what we can do. First and foremost, we want it to Cripple, and we want it to deal damage based on how long they've been under the effects... that's doable. Let's see....
Strike of Infinity (Channeled):
After X(1-2) seconds Cripples all units in an AoE for Y seconds. Then begins to apply randomly the other 6 conditions for Y seconds, until all are applied (applies a new one every Z(2/1.5/1?) seconds). Once a unit has all seven conditions, it is dealt Z damage. Lasts just long enough to take a non-conditioned unit to having all 7.
Meh, seems a bit much and a bit wonky, but with cleaning up it may be worth something? I'm sure you can work something better to be honest, but i'm just throwing it out there anyways.
Overall (although it may be hard to tell from all the above), nice hero. There are a few things here and there that you'll get used to with DoE such as the way conditions interact and the lack of anything but conditions, but you show promise. Hope to see more of your stuff here (but don't expect so long of reviews... i'm just up late because I was supposed to be observing 9 Metis tonight, but it was too cloudy).