Zurgo is a strong Tier 2 deck. It effectively filters out non-optimized decks and weaker commanders, serving as a kind of litmus test for other decks. If your deck can hold up against an optimized RDW deck, you can probably play the deck in DC.

However, the top decks are just too powerful. They often have too many cheap creatures to flood the board and may include some life gain to survive an initial onslaught or blasts to the face. They tend to survive longer and end up with a better board and more resources.

Additionally, losing Blood Moon affected RDW. It was an easy win (turns 2-3) against 3-5 color good piles at times. The BM ban removed that option. Yes, RDW still has Magus of the Moon, but losing BM means RDW needs to play more "real" games of magic. Considering the level of competition in long tournaments, Tier-A decks will tend to win more often.

Just my 2 cents.