That's not exactly true. Just drop Rag after you clear their board. No more RNG. Or clear off the minions except for a 6/6 or whatever. Now it's either Rag hits for 8 to the face or clears the minion. And if you're the other guy who had an abusive sergeant in hand, and was holding your fingers crossed Rag would hit to the face, maybe try some other cards in your deck instead. The RNG from Rag is fine, and there's plenty of answers in the card pool for one if it is played against you.
In the case you describe the game is probably very one-sided, you play Rag against a board with 5 creatures, you still lose next turn to a Savage Roar combo, Leeroy + UTH, etc. You accept what Rag is when you play it. If you need to swing for the best case scenario when you play it, you've probably already lost, and if you play it when you have board control, you might actually regret it (in the case of Faceless + BGH, etc). It's not a badly designed card, it's useless as often as it is useful, a late-game card that needs some care to perform optimally.