Personally I see Sweltering Heat work quite well, perhaps making it so the target can't sprint or jump when it's on them would help for PvP, but in PvE I find it very very very effective. In PvE a pyro's key to survival is staying mobile and timing there CC with their casted attacks, which isn't usually a practical option in mass PvP anyway. My suggestion is you spend your two points somewhere else if you're a PVPer and you don't think it's effective, I'm sure there's something you could find more helpful to you. Just because it's there doesn't mean you have to use it. But like I said I don't see why a debuff preventing movement enhancements for 2 seconds would be game breaking for the glowbat crowd so I support it.
I would think adding a 2 second damage debuff to targes popped with Infrared Scanners might make it more attractive, pretty much everyone I know just doesn't use it for the same reasons you already pointed out. Your chances of popping someone out of stealth <10 meters and having the reaction time to do anything helpful for yourself is pretty much none anyway. But again, that's two points you can throw into something else.
I don't like your suggestion for Degauss because of Pyro mechanics. Fully talented a pyro can have shields up over half the time in a heavy fight due to the cooldown reduction when taking damage. That's just too much defense against what is a major skill for many profs. I also think adding the previously discussed no movement enhancements debuff on Sweltering Heat would help greatly with the people constantly jumping onto your face issues.
I don't believe making one prof OP just to spite another.
I also believe some talents are primarily intended to enhance PvP while others are intended to enhance PvE. Pick and choose what works best for how you play and go with that, for example I pretty much only PvE now, so I have no need for infrared scanners and thusly didn't waste my points on it.
Sweltering heat isn't a bad concept, its just a bad execution. 30% just isn't enough. If it was 70% then it'd actually be noticeable. Or 30% for 6 seconds. Currently for us pvpers (which i thought it was primarily for) it just sucks.
I honestly don't think pyro needs a damage buff, so i'm meh on that point.
Understand that aside from Electro Dart, Pyro has no utility vs all other classes. Sweltering heat won't slow anything down enuff for it to not still hit you. the rage spec for the majority of juggs and marauders mean our knockback is instantly countered and effecively useless. Vanguards/PTs have grapple as does shadow/assassin to also close distance. My point is, every class has an "answer" to our knockback, while Pyro has little to nothing to respond to any other AC's abilities aside from damage.
Degauss making it so they can't be lept too means *gasp* they won't focus you first for a change! They might actualy pick another target they can leap to.
You primarily pve and i respect that. But i pvp ALOT and i have grown tired of every melee class within leaping/grabbing range auto-switch targets to me even over a healer simply because when focused, we have really nothing to deter their advance. I would like to stop being the easist class to kill.