Sabo vs Burgess was a Zoro vs Lucci thing, he had to be occupied by someone so it's justified for him to not just whoop the main villain and/or his subordinates. Fact remains that, when they got serious, they neg diffed their opponents easily.
Sabo even permanently disfigured half of Burgess' head and had him in a near death state while Sabo himself was clean.
Also, Sabo could match Issho (although Issho was holding back).
Plus he's Dragon's RHM.
I'd bet on him beating Doffy's ass hard in Dressrosa, he was probably on King or Katakuri's level once he got the Mera and above when ever he masters/mastered the fruit