http://www.cubetutor.com/viewcube/12765

It's a general-purpose cube. I want to avoid unimpressive curve-fillers like Canyon Minotaur, but also avoid pricey and/or overpowered cards like Time Walk. I want a decent chunk of the cube to be artifacts, similar to Scars of Mirrodin block. That way, you can draft without shoving yourself into some two-color combination right away. Also, there is some monocolor support, such as Corrupt and Dungrove Elder. Not sure about what portion of the cube will be multicolor, I expect to cut down on multicolor quite a bit. And of course, I want the amounts of each color to be relatively equal.

I want it to be a fairly aggressive environment in general, to the extent that the colors with the better lategame options are balanced against colors like red. White, Black, and Red all have a fairly aggressive slant, although white and black both have other good options as well. Blue is more tempo than control, and green is dedicated ramp when it isn't going full enchantment mode. Colorless cards are pretty focused on being either ramp/fixing or aggressive (for R/W decks).

I'm not sure I have Dimir quite figured out, but other than that pretty much every 2-color combination has some kind of synergy / draft archetype. To copy-paste from http://www.cubetutor.com/cubeblog/12765 :

Azorius: Tempo (Enter-the-battlefield)
Dimir: Tempo (Evasion)?
Rakdos: Aggro (Vampires) - My main concern is that including cards like Bloodcrazed Neonate drags red down. I'd prefer B/r vampires to be the archetype rather than monoblack vampires, but I'm not sure how well that works out.
Gruul: Aggro (Power Matters) - A bit of an all-in theme. Basically, you combine cards like Ooze Garden with power buffs like Colossal Might.
Selesnya: Enchantments - Whether it's putting Auras on something or winning with Sigil of the Empty Throne.
Boros: Aggro (Metalcraft)
Simic: Counters/Proliferate
Golgari: Midrange (Self-mill)
Orzhov: (Small Tokens) - Not a ton of token support in black, it seems.
Izzet: Instants/Sorceries

Thoughts? What archetypes could use buffing/nerfing, what cards are insanely-powerful bombs and which are last-pick-every-time, suggestions for cards to add?

I would advise against making vampires an archetype. I just don't think that there is enough tribal synergy to make it good, and you end up having to include some really bad cards like neonate.
If you want orzhov to be tokens, give white the token makers and give black sac outlets or morbid triggers to exploit those tokens.

With all the signets and all the bounce-lands, you have too much easy mana fixing. I tried this once in a cube and it ended with not needing to make meaningful choices since it was too easy to play a five color deck with all the best cards you picked.

~SE++

Hm. For the mana fixing being too easy, would just dropping the Signets make it alright? I don't want it to be that easy to go 5-color.