4|3 
sounds right for a spell to draw 2.
Fixed. Thanks again for your unvaluable help.
Effects can't just be simple addition. For example, immortality. 6 
for immortal in which it does 4|3. Phase Dragon which doubles (8|6), costs 13 .
Another reason is because you're stuffing all the good stuff in one card, and you can put 6 of them, which means you can draw a total of 18 cards.
Effects can be simple addition unless there is a reason why they are not.
Immortal is a skill that is not simple addition. Instead it is valued as a function of the opponents desire to target it with CC which is a function of the threat [Attack+Skill Value] of the creature.
Additionally HP is not valued on a point by point basis. 1-5 HP is worth 0 quanta and 6-7 HP is worth 1 quanta.
6 cards in a row that can draw 2 cards each nets you 6 cards not 18.
6x2 (cards drawn) -6x1 (cards played) = 6x1=6.
Now for the reasoning why Drawing cards and Deck thinning are likely to be simple additions.
Card Advantage (Drawing Cards):
Unless a card is OP or UP they all have balanced cost to play. Thus the card advantage of each card is about the same because the difference in value is already accounted for in the other costs. (This is not true with every card but it is true for the majority)
Deck thinning:
Deck thinning has only been found in an added on form (Sundial, Precog). It is fair to say that we can use a Deck Thinning 1 card as the base to add more effects onto.
