What? No.
I respectfully disagree.
I find it interesting that you say that to be perfectly honest.
The most efficient possible play at 4 drops will always be a singular 4 cost card. No matter what two different 2 drops are capable of doing, they will never be as efficient as the equivalent ability(s) and cost(s) on a single card. That is to say, it is always better to pay 2 mana and deal 2 damage using one card than it is to pay 2 mana and deal 2 damage using two cards. The only difference at that point being the card itself. And when that dichotomy is understood, it becomes apparent that the most valuable resource in any card game isn't mana, or life, or damage; it is the very cards themselves. The most efficient possible imaginable play at 4 mana will always in theory, and often in practice, be a singular 4 cost card.