double blue is very difficult to get for the combo decks that would otherwise abuse it.  In order for the card to really work, you need a manabase that can produce blue consistantly, and cards you don't mind discarding EOT, or the ability to empty your hand every turn.  The only decks out there right now that fit the bill are Bazaar lists, more CA than Dragon.  It might be okay in a madness list, but the mana is tough to get there.

Oh, I definitely agree with that.  It's definitely possible to put together a deck you can win events with without Drains, it just takes a little tuning.  However, I feel that the optimal builds of a Control-based Oath deck are going to include them, and that anyone reading this thread should realize that a Counterspell build isn't ideal.

If your heart is set on an aggressive combo build of Oath- here's my suggestions:

Colossus is probably just better in most matchups, most decks can deal with Plats in the extra time you give them. 

Timetwister's a nice enough card, but nuking your graveyard could be too big a drawback, even with Force-pitchabilitty, Wheel is probably just better, I'd use the slot to test Ideas Unbound for now, though.

I'd probably cut the regrowth, unless you want to add Gifts Ungiven to the deck (which could be a way to go, but I'd imagine you wouldn't like the cost if Thirst is too much for you)

The manabase is definitely taking up too many slots, I'd cut 2 or 3 sources right off, possibly to test Ideas Unbound at first, which does feel strong in a deck with so many cards it doesn't mind discarding (LED/Spellbombs/Colossus/extra Oaths).  Personally, I think Library just lets you win games you otherwise couldn't, but I find that's really a playstyle call

Are you allowed to play a sub-optimal list? sure you are.  Nobody's stopping you from playing Trash for Treasure over Goblin Welder in Control Slaver either.  If you're just asking the community's permission on wether or not you can play a suppar list, you really shouldn't have bothered- most of us would be happy to play against it.  If you're interested in what's optimal (which is really the only reason you should be posting in the first place) then Mana Drain has it by far.  You could build a version of Oath that doesn't want Mana Drains, in theory, but that list with that many sinks most definitely does.  For the record, if you reworked the list so that Mana Drain wasn't solid, running something like Duress or Daze would probably be a lot better in that slot than Counterspell.

Gro is really the only deck the card would work in.  An Arcane Lab deck wouldn't be built to cast four spells in the same turn, and god knows fish can't.  The card isn't really a great disruption element for Storm combo, because the other player will just burn a brainstorm and counter your threat.  It *is* a great card, however, just for slowing down another player's strategy, and only time will tell how good it is at that (though I'd imagine it's amazing).  A Gro style deck would really be able to abuse all of the aspects of this card, wether that pushes Gro into the playable category-  I guess we'll see

I think one people might not be understanding is that WTF is a classic tempo deck, in the style of RDW, where U/W is more of an aggro/prison deck, and cards that are amazing in UW Fish, like Rootwater Thief and Voidmage Prodigy, just don't make the cut here.  Your gameplan with WTF is purely to slow down the other player with mana denial, while cost-efficient creatures put them in a position they can't recover from.  If you're holding back mana to activate Thief or use VMP, you're not going to be able to apply the pressure you need to keep your opponent from switching to a beatdown role.  Poor Cost-to-Power ratio in a deck that doesn't want the Prison elements fish has is the same reason Flying Men would be terrible in the deck, and why Spiketail Hatchling isn't pulling it's weight here.