As long as Brûlée solos, I'm unconcerned.
On a serious note, that's complete nonsense. Mama sending Cracker only means she's acknowledging Luffy's strength, it's not implying in any way she actually believes Cracker is stronger than Doflamingo - there's no way she could possibly know that. When sending him out, she also knew that Brûlée would still be there as well.
That Bounty's no implication, either, considering Doffy's was simply frozen, and the WG had no idea of his deeds and involvements with the black market. That man was delivering weapons and drugs all over the world, funding multiple wars, and was running the biggest underground black market place. An illegal research lab as well, supplying a Yonkou with artifical devil fruits and weapons of mass destruction - and by the way threw over an entire kingdom, enslaving its inhabitants in the process. I'm certain Doffy's Bounty would exceed even Jack's had all these things been known.
Going by portrayal, Doffy is easily above Cracker, considering the ease with which he used Parasaito on Jozu, who's also a high-tier of a Yonkou's crew. Bullet Thread gg.