You don't need to make the Warlord a 6/6. 5/5 on one minion is better than 4/4 + 2/2, imo. You can't look at the total stats of a token minion. It simply doesn't work that way. You can kill the Silver Hand Knight in pieces without actually losing anything if you have a 4/5 and a 2/3, for example. But you'd have to trade them for the 5/5. In this sense it plays more like a 4/6 than a 6/6. Further, to remove the 5 damage threat, you need to deal the full 5 damage, while you can reduce the damage of the token combo by killing either part. For the most part, the token is really inconsequential. You're not losing any sleep over leaving a 2/2 on the board, but if you have to leave a 5/1, you're a little more scared.
Token minions are good when your opponent's board is clear. It's hard to remove 2 things with just that much mana out of hand. Usually you'll at least have the token left, and if you can buff it, you're solid. But if there is anything on your opponent's board, they will often be able to find a favorable trade.
Yes Silver Hand Knight is still better than Warlord in the worst case, since it always at least gets the token, but it's never great, and Warlord can be. If you make it a 6/6 or a 7/7, even by playing multiple cards on a late turn, it can be a game-winner. On my expensive cards, I'm willing to take that tradeoff. On later turns with more mana available you often have choices to play something else, so you're able to avoid the worst case a little more often than with the cheaper (2-4 mana) cards.