Unless building specifically for a highlander (only one of any card allowed) game, the following tenets apply to deckmaking:
1. Multiple copies of fewer cards lend to greater chances of drawing what you want when you want it. Reliability can be a good thing.
2. Slivers are only good in large quantities.
3. Watch your mana curve (yours doesn't look too bad, actually). By this, I mean have a good spread of casting costs (cc) -- for example, 10 1cc, 8 2cc, 6 3cc, 2 4+cc. This allows you to have a good chance to play what is in your hand.
4. Ask yourself why each card is there, and if it can be replaced by something better or more versatile. Using Arcane Denial(AD) for example, are other counterspells a better choice? AD lets your opponent draw cards, which is generally bad for you (as your opponent then has more opportunity to draw his winning card). Your deck currently has enough blue to support other counter magic that has UU in its casting cost. Counterspell is by far the best choice (I am sure that will spark some comments...), and as you already have one, I suspect you can get more.
5. Card synergy is important. Aside from being a really cool word, synergy means (roughly) "works very well together, in numerous ways".
You have Soul Barrier in your deck, so I will use that as an example. Soul Barrier forces your opponent to pay extra mana or life when casting a creature. Two ways to maximize this are to tie up his land, or continually put creatures in his hand, forcing your opponent to recast them. Black offers Rain of Tears and Despoil (among others), which both destroy land. Blue has Psychic Venom (2 damage whenever target land is tapped), as well as numerous ways to tap someone's land (Drain Power, Mana Short, etc.). Both of these methods tie up his land resources. Blue is also the king of bounce, Boomerang, Snap, Capsize, etc. all put creatures (and sometimes other permanents) back into hands.
Once a card is in someone's hand, you can counter it (provided you've counter magic at the ready) with blue spells or force a discard through black spells. Supposing they get a creature out despite your best attempts to prevent it, black has more permanent creature removal, such as Expunge.
Once you have removed your opponent's blockers (even if only through tapping them via Rhystic Deluge), hit with your creatures for the kill. Should your creatures force discard (Order of Yawgmoth) or a bounce effect, then so much the better. All of these cards playing off of each other are a form of synergy.
6. Do not use mutually exclusive cards. If your deck packs a lot of land destruction, don't play with cards that give your opponent land, such as Veteran Explorer, Hired Giant, or Oath of Lieges. This only defeats itself.
7. Use artifacts to supplement your deck. If you decide on discard as a primary method of disrupting your enemy, then consider Disrupting Sceptre (an example).
That should be enough for now. Rethink your deck, and when you have a better idea of what you want, let us know, and we will happily help you with it.
