Hearthpwn

So thought about this a bit more, changed my vote from Playable to Bad.

There are a few ways to use Prismatic Lens.

You "could" plop this in a normal deck and hope for the best, that a good card isn't ruined. However 4 mana draw 2 isn't great although Paladin does lack draw; also the risk is just too high, so it won't see play this way.

So you start cheating.

1. You put this in a deck with cheap cards. Cheap minions, cheap spells (e.g. BoK). Whatever comes out is still usable. Main problem: Divine Favor is just better.

So you start cheating some more.

2. You put this in a deck with cheap spells, and expensive minions. Problem: the deck becomes wildly inconsistent. You are also hoping that aggro pretty much does not exist; because if you meet one, you ded. You ded ded. Even in the optimistic scenario that you draw this early, doubtful you can fend off aggro til t4 at the earliest with Paladin cards. People seem to think this might work, but it won't. Noble Sac, Humility, Lost in the Jungle; apart from these you can't do shit. These are really bad defensive options. And unlike Priest, Paladin can't cheaply re-use minions (Resurrect).

3. You put this in a deck with cheap minions, and high cost spells. This is more realistic. However, consider the following:

A. Far Sight is widely seen as a comparable analogy to this card. Far Sight has also never seen play in aggro. It has only seen play in combo. (with the caveat that Far Sight would have the risk of pulling something 1 mana and not get a discount while this tutors a high cost spell from your deck. Ultimately though Midrange has never run this either.)

B. The card costs 4. You are paying 4 whole mana upfront with this card, to draw a card. That's expensive, for aggro. You never see aggro Paladins playing Divine Favor early. You will lose tempo, and you will lose. This card costs 4 upfront. People think "play this t4, t5 Dinosize gg" when if you play this t4 you have effectively skipped t4 and given the opponent a huge break to stabilize. You can rarely afford to do this. Most likely the card will be kept in the hand until you start floating mana as an aggro deck like t7~8ish. By then a Dinosize play isn't that great.

I have found a use for it. In a jack-of-all-trades paladin and potentially only as a one-off, this card can act as Arcane Intellect in Mage, except that it can occasionally get you an empowered combo. It makes your opponent less certain. In such a deck, the extra 1 mana cost can be justified in that it wins you certain games. It errs a bit on the side of win-more, but if your plan involves a lot of stalling, that can be a good thing. For example, I like to run Deathwing. It is a nice all-in card, and if I can play a robotic egg the same turn as Deathwing, I get 20/20 in stats on 2 bodies, occasionally before turn 10, with a board clear. Pretty neat, especially if you do run its (better) cousin Divine Favor.