Also I would like to point out that having organs damaged doesn't effect the ability to use Haki or string abilities as far as we know, both of which make up the majority of Doflamingo's power, so saying that he is vastly weakened is silly.
And even though Doflamingo is weakened the power Luffy has in Gear 4 is completely over powering him, he could beat him in Gear 4 regardless of if Dofalmingo was previously injured or not.
G4 Luffy has Doflamingo completely out matched.
Actually, it can hinder his ability to use his strings. While the strength and quality of the strings may remain the same, Doflamingo wields them by swinging his arms and legs. His ability to move is gonna be hindered by not only the pain, but also the state of his organs. He stitched them back together, but the pain hasn't gone away from when they were separating, along with the pain of them being dragged back together and pierced by strings. The flesh hasn't fused together either, they're just pieces somehow functioning because the strings are holding them together. It's not unreasonable to assume that it's gonna be a continuous process of stitching due to Doffy's being hit and thrown about by the force of Luffy's punches. Not to mention Gamma Knife damaging him internally is gonna also damage muscles around the organs, so they're gonna be sore and not functioning to their fullest potential. Organs are required to move. He's not gonna be able to swing with the same amount of force as much as before, and if he does, it's gonna cost him by adding strain to his body. Observation can be potentially hindered, as concentration is required to maintain and use it. Surges of pain from his damaged organs and muscles can dip his concentration, but that really depends on how well his pain tolerance is, and it's probably pretty good.
We don't know how Doffy with his full power would fair against G4 at it's full potential. We also shouldn't take these initial scenes of Doffy being thrown around to mean it's gonna happen throughout the entire fight. Lucci was also thrown around when he first faced Gear 2 and 3, and that was an extreme diff fight to the end for both men.
Luffy also blitzed Doflamingo with Rhino Schneider. Gamma Knife didn't damage his eyes at all, so Luffy moving so fast that Doflamingo can't see him would also be the case if Doflamingo.
His reaction speed has taken a notable and clear dip. Prior to Gamma Knife, Doflamingo was able to notice and physically react to Luffy's Jet attacks before they struck him, a clone was able to swat away a Jet Pistol. Now, Doffy wasn't able to notice a Jet Bazooka until it was already at his chest.
