Wow, thats what we in the biz call a "radical interpretation of the text."
The Bannertech Gamma Dome (appropriated from Amadeus Cho, who originally was shown using the tech in INCREDIBLE HULK #109-110, before it was used in Gammaworld circa WARBOUND #1-5, then altered by Banner around INCREDIBLE HULK #604) only disables the tech *within* it, not outside--hence, it did disable Doom's armor, at least initially. It did NOT disable the castle's weaponry as that lay outside the scope of the dome.
Does Doom have backups? You bet. But I'm guessing the time it takes for them to go online was less than the time he actually spent in the dome with Banner--long enough for the effects of the poison in the Hulk robot to take effect. Once the dome disappears, Doom is free to use his armor again, whatever the case--but his diminished mental faculties are such that he can't use several of the more advanced capabilities. (It could also be that the poison of sorts was already working, clouding Doom's brain and making him think he couldn't use the suit. Who knows?)
Whatever the case, Doom DID underestimate Banner. And Banner's smarts have been long pushed to the background as he's had a more pressing problem to deal with--the Hulk.
The biggest thing Banner has in his corner now is the element of surprise. Everyone's forgotten what a formidable genius he can be. And to combine that quality with some of the worse aspects of the Hulk's personalities...well, Banner is one spooky character.
I agree that Bruce's tech has to come from somewhere. Yes, the Leader's lab, that's likely. He could have taken some of those funds Amadeus Cho took from the Angel (INCREDIBLE HULK #107). And if he's anywhere near as proficient with numbers as Cho, I'm sure he could make a minor killing playing with some stocks or such. Or maybe others are lining his pockets.
Banner has manipulated and disabled machines outside of the gamma dome, so he isn't limited to working within the confines of the dome.
However, you're correct. Since my copy of the issue hasn't arrived, I was going off memory of the scans. Looking back at them, it's obvious that Bruce used the bubble to buy time for the Leader's anesthetizer to take full effect and leave Doom defenseless.
Now if you're trying to convince me that Banner is in the same class as Reed and Doom, you're preaching to another preacher.