Savage Hulk stood up to Glad's heat vision for quite a while. He was completely unharmed by Fing Fang Foom's acid-fire breath. He's taken Human Torch's nova blast with absolute ease. So his limit in heat-resistance is impossible to gauge. If he had even a scratch on him, we could say he could only take so much. But that he was completely unharmed. Hulk could very well survive in the Sun. It's never been said he couldn't, has it?
World Breaker is >>>>>> WWHulk, and of course with the amp would come a seriously amped HF. I really don't think BFR to the Sun would kill World Breaker. If anything, when he starts to burn the closer he gets to it, it'll just keep angry and amped. The only problem for World Breaker would be how to get back to Earth. Or maybe he could thunderclap the Sun to screw us all.
How the Hell does his HV get hotter than the thing that gives him power?
In any case, my point is that we have no idea how much heat the Hulk can handle. Red Hulk, as standard, crystallizes sand into glass, which is about 2000 degrees, and even when Red Hulk got hot enough to feel faint, Hulk was completely unharmed. Planet Hulk was also completely unharmed by the core of Sakaar, which is likely around the same temperature of the core of Earth. About 10,000 degrees. The temperature of the surface of the Sun. So, at minimum, we know Hulk could survive entry into the Sun. Savage Hulk was burned by Glad's HV, true. But there are many stars that can get as hot as 250,000 degrees K. That's far past the surface temperature of the Sun. And to top it off, Hulk has survived unharmed by a ground zero nuclear explosion. Nuclear explosions reach temperatures of 10,000,000+ degrees K. The core of the Sun is on average calculated to be 15,000,000 degrees K. At those temperatures, I doubt an extra million degrees or so will make a difference.
Since Savage Hulk survived the nuclear explosion, it's safe to say World Breaker takes BFR to the Sun just fine.
Superman lacks the damage output to take WW Hulk out. If we take a look at everything Hulk has done, since he has been created and everything Superman has done post retcon... Hulk's durability > Superman's damage output. He is much faster than Hulk and has the versatility but in character he won't do something like phasing Hulk's heart out or some weird crap like that.
WW Hulk is Hulk with a massive amp. Stronger and angrier than he has ever been before. Superman without some major sundipping action won't do all too much there, just like Thor wouldn't be able to do all to much and so on.
It takes someone of Sentry's caliber to achieve something in such a fight B-)