One... Well, TWO words:
Leviathan.
Mastery.
Waterspout is awesome for adding damage, it's up about 30 sec on 30 sec off with 3 SO rech slotted and about 72% global rech. Does excellent dmg over time, and it does knock UP instead of tornado's (which it is otherwise a slower recharging clone of, albeit with better FX) Knockback. Excellent power. It even causes FEAR (so it fits in perfectly with the Shades etc), AND gives you your only -Def power! As a Dark/Time you would likely get a much better up/down ratio since you have (or will soon enough) Chrono Shift.
Lev Mastery also gives you Bile Spray (decent cone AOE that meshes well with FS and Living Shadows), Hibernate (if you want a panic button it's a great one esp with all the pets and pseudo pets you have), Shark Skin (pretty standard Res based APP/PPP armor) and summon Coralax (decent dmg pet with a cone that meshes well with the cones you and Umbra beast have IIRC as well as melee attacks.).
I vacillated for quite some time, but finally bit the bullet and made the trek to the red side and back... Well, ok, I went to the red side the hard way, I payed the paragon Points for an express pass back to the blue side. 
I've been very happy with Lev Mastery, seriously, it's excellent dmg esp when fighting single hard targets like EBs, A/Vs etc.
Granted this is from the perspective of a Dark/Dark, but it should be equally applicable to a Dark/Time.
::tosses two shiny coins in hat::
Arg
I tend to go with the patron pets on my controllers - but I build them all for perma-patron pets as well, so if you don't go for that much recharge it may not be a solid option.
My reasoning is generally that I have "enough" to do between my primary and secondary that I don't have as much time for just "blasting" as say, a dom, with the 1-2 extra attacks an epic pool might give.
I particularly like the /soul pet - she does psi damage and has really solid range, so she just sits back, safer than the other pets, and blasts away. I've heard really good things about the /mace pet as well, but I haven't used it in a while. Plus, mace comes with the s/l/e shield and a -res res debuff that does solid damage (poison ray) - if you really want an attack. The drawback is, of course, the redraw on the blast (and the theme, if you hate it).
On my dark/dark I went /soul. I took Dark Embrace with the base slot, and Dark Obliteration for some extra AOE + Summon Seer. FYI, Dark Oblit damage is = fireball sans the dot (27.53 unslotted, @ 50. Or about 100 with containment, I think) + a -7.5% tohit debuff.
Guides: Dark Armor and IOs | SS/DA | Crabbing | Fortunata
I will do what I do with almost all of my others and get Scorpion Shield. I will get the Clarion incarnate that does power boost for a longer duration.
(Slowed Response does -defense as well.)
YMMV---IMO
Ice Ember
Enjoying the daylights out of my level 36 dark/time troller, but I'm a bit torn on epics. I have control up the wazoo and more tools than I can realistically use every combat, but I lack damage. ATM, I've taken the Fire epic to help with this, but if I stick with this, I'll miss out on Powerboosted Farsight which makes me a little sad. I know I can't have everything but...
Is there another damage option that approaches //Fire? Barring that, is there another APP/PPP that I should be considering for reason X? I'm actually willing to try anything, I just need an idea. I can always use a dual-build (one teaming/one solo,) but I'd like to hear input from the peanut gallery if there's a great idea I'm overlooking.