Don't have to imagine anything as it happened in manga. And no it wasn't as bad as you're implying it to be. He was just blocked and I don't understand why you guys are making big deal out of it. An admiral was wounded to a level where he'd bleed yet it doesn't seem like ridicule to anyone but just immobilizing Jozu made you believe that he's stronger than Jozu. He was attacked out of nowhere so of course he'd wonder about what happened to him hence the bubbles with "! & ?" symbols. He was blocked and half of the conversation was over before Jozu looked back to see by whom he was stopped and the rest of the argument was ended and Crocodile landed an attack as soon as he turned back and I don't see why the conversation would last more than a few seconds.
Getting attacked off guard is very casual thing when you're in a battle. Hell even Akainu was cut in half by a fodder ass like Crocodile that too when he was fighting Jimbe an absolute fodder against him. You're not going to tell me that he's weaker than Crocodile? So before calling Jozu weaker than Doffy you'll have to admit that Jozu > Aokiji and Crocodile > Akainu as their situations were just as bad as that of Jozu.
G4 is G4? What is the supposed to mean? G4 or not he's in a weak state which means that he's weak regardless of the mode he's using. G4 doesn't make him healthy or restore his power. If anything it makes his condition even worse. It was just that he raised his limited power to it's maximum. I am pretty sure none of his attacks(as far as his devils fruit is concerned) were noted be weakened because of his condition. When it comes to physical traits Jozu is like someone with G4 on 24X7 so ya he can break out of it. Why would he get caught in the first place? It's not like Joker would get the luxury catching his opponent when he's off guard as it is not going to happen in a one on one battle.
Once again Doffy immobilizing Jozu means nothing in a one on one battle and I am not going to repeat same wall of text again.
You keep saying the same thing, that Doffy restraining Jozu means nothing in a one on one fight, yet you assume that Jozu can break free from parasite(something that holds no ground whatsoever based on the manga). That's basically denying the only point Doffy has on Jozu. As of now, based on the manga, it's Doffy 1 - Jozu 0. If he's done it before, then he can do it again. Jozu was unable to break free, end of story. Parasite relies on 2 big factors. Brute strength and willpower. If Oda wanted to show Jozu's superiority he would either not have him caught in a web like an insect or make him break free. He was vulnerable at the time, and since he couldn't break free, I can assume that Doffy could've harmed him if he wanted to.
Now, if you really insist doe, I can go with your flow. Let's just say that Doffy can't restrain Jozu via parasite. I've mentioned before that parasite relies on 2 big factors. Brute strength and willpower. I don't think Jozu lacks the strength, so the thing he lacked was willpower. Also, in order to get the parasite through, Doffy bascally penetrated Jozu's defenses so that means he used haki(Since Jozu was on his way to attack crocodile with the diamond and haki coatings on). From that, we can assume that Doffy's haki is better than Jozu's, so now he has a way to cut him down. And since Doflamingo's agile and faster than Jozu, that basically means that he can dodge Jozu's attacks and cut him down
without parasite. This scenario goes to show that even if you deplete him of his feats and arsenal, Doffy still has the means to beat and harm Jozu.
Oh and about the the admirals and the sneak attacks. What did Aokiji do after he got punched ? He shrugged it off and proceeded to one shot Jozu. Similarly to how Doflamingo just spat some blood after he got Red Hawk'd(It was just a superficial injury, so that's a durability feat as well) and then went on to wreck Luffy and Law. Akainu. Yes he got attacked by Crocodile but what happened next ? Akainu was ambushed by the WB pirates so he didn't **** Crocodile up. Now what did Jozu do ? Completely nothing. He just sat there helpless and then got sables'd away. He didn't retaliate, so that means 2 things. He either couldn't do anything or he simply chose not to do nothing, which means he's a mazochist. Up to you to decide what really happened.