Ok - I think that your build is okay - but, in practice, you're going to have some challenges. One of the things that's great about Mids' is that you can slot your character level by level, instead of as if the character started at 50 and you've got to plan everything with the final picture in mind. A final picture is great, but if I were you, I'd consider changing some things up.
These are mostly my preferences based on bringing an ice/ice and a Fire/mental blaster to their highest incarnate levels. Really loved playing both - I miss 'em, I do.
Anyways - a few points to consider.
1. Hover is a great mule for the recharge proc. But, you've already got flight - why not take hasten for much better recharge at level 6, maybe toss the hover in at some point after stamina is fully slotted. My reasoning is that higher recharge rates requires more endurance. Drain Psyche will help a bunch, but you don't get that until level 20.
2. This is just my rusty gut thinking, but I see you've gone for Dark Embrace, a resistance power, as opposed to a defensive one. I'm guessing this plays into the very cool name of Nightshivers. If not, I'd encourage you to go with a defensive set. Your s/l defense is pretty low. To get in the midst of a group to use drain psyche, they don't always all get locked down (if you have a controller on your team) and confusion is a power that is hit and miss in it's effectiveness and duration. This is why I'd recommend you choose SS over fly, keep hover if you need vertical access, or combat jumping for more defense. SS with the celerity lets you zip right in the midst of a mob for drainpsyche to disorient the mob and refill your endurance bar after using it all against the last mob you clobbered. It's a preference, probably, and that's all well and good, just figured I'd share my two cents about that. (for free, what a bargain!)
3. The medicine pool - If you like these, keep them. But, if you just liked the bonuses, there might be better ways than using medicine pool.
4. Stamina and endurance. So very grateful the fitness pool is now inherent. However, in my play, I recall always needing endurance, unless I'd gotten some buff from another player. SB, AB, that kind of thing. That may have been my playstyle and liking to keep SS on while I fought. If memory serves, I like to have my recovery be about 2.0 per second higher than my end drain. Just a personal rule of thumb. Maybe try to slot stamina a little earlier.
5. My biggest concern is not knowing your playstyle. If you anticipate entering melee range for drainpsyche, I'd really like to see you boost your melee defense, or boost your s/l defense. It's certainly possible to do so, but most sets won't boost defense and recharge. You kind of have to choose how to balance what you want - and it's best to adjust your plan as you level up, based on what's working while you play, or what's not working. Something would have to give, sadly. Does it really make that much difference? Not really sure, but I suppose you could always eat the purple candy.
It certainly seems like it would be a great character to play and level. I hope I remember to make one of these myself. Hope you get to try this one out really soon!