Sure they were.
1 Gorosei and 1 Admiral are already big problems for a Yonko.
Imagine sending +1 more Gorosei and +1 more Admiral.
Also, Saturn was confident he can take command of the Island's defenses because he has higher authority than Vega Punk.
The entire Marines + Warlords fighting the WBP was a show of strength, and honestly without outside interference, not only Ace would've been executed at the Platform but also there wouldn't even what they've called WBP Remnants, they would've been eliminated there.