I believe you have misinterpreted events.
The Daleks are extremely racist, and absolutely convinced of their own genetic superiority. By definition, they believe all other genetic lines to be inferior, and further they believe fully that all inferior lines must be destroyed.
The hybrid Daleks are the epitome of self-loathing racists -- they are "impure", they know this, and they despise themselves for it. "Rose's" Dalek in the episode Dalek is a perfect example of this, although he seems to be more capable of accepting it than Daleks we meet later.
The hybrid Daleks want to be destroyed to eliminate their own impure DNA from the universe. Thus, when they succeed in creating "pure" Daleks, and those pure ones decide to eliminate the hybrids, the hybrids agree with this assessment and allow themselves to be destroyed.
Further, though, we know from Daleks in Manhattan / Evolution of the Daleks that Dalek weapons are fully capable of overcoming Dalek shields and armor and destroying Daleks:
We see the enslaved Dalek humans turn on their masters and destroy them with Dalek weapons, even while those Daleks were actively resisting their own destruction and fighting back.
The hybrid Daleks did no such thing -- in fact, IIRC, at least one of them says that he agrees with the pure Daleks before being destroyed, so I think it's quite believable that he deliberately disabled his own defenses in order to make his own destruction easier.
All that said, the reaction of the Doctor -- and the accompanying dramatic music etc. -- do lead us to think that the new pure Daleks are more dangerous. Not more powerful, but more dangerous. Why? Simply put: They don't hate themselves. They are pure, they are superior (to their way of thinking, of course), so there's no wishy-washy "Destroy everything else, but I also have to be destroyed" thinking going on for them. (Although a counter-point is previous statements from the Doctor implying that the self-loathing Daleks are more dangerous, because they hate themselves. So, not really sure which way it really goes here -- maybe the Doctor believed that until it was no longer academic and he was facing pure Daleks.)
In answer to your second question: Nope. At the very least, the Dalek in the episode Dalek, the damaged one that the Doctor and Rose encounter in what's-his-name's vault and that Rose accidentally reinvigorates with her touch, was pure, a survivor of the Time War (at least until it incorporate Rose's DNA and became impure, of course). We also see other survivors of the Time War, such as those who escaped in the Void Ship -- they, too, are pure. Until the creation of these pure Daleks, all Daleks created after the Time War are hybrids of some type or other, yes, but those that directly escaped/survived the Time War were pure, as are the colorful new pure ones the hybrids managed to create.
