I think it’s easier to accept if you look at it as he did, which is that Hybrid Sek was a chance to turn the ruthless persistence of the Dalek factor into a force for good.
You can find a similar reasoning in the Doctor’s comment to Sarah at the end of Genesis of the Daleks about why he’s not disappointed at failing to destroy the Daleks.
“I know that although the Daleks will create havoc and destruction for millions of years. I know also, that out of their evil, must come something good.”
That said, I can see how the Doctor behaving as he did prior to the new series doesn’t follow the current path the character is on.
The Doctor was heavily involved in the destruction of the Daleks and the Timelords, as per the new series. The 2005 episode Dalek involves a Doctor who willingly tortures the last Dalek when given a chance and has to be stopped by Rose from shooting him down during the last standoff.
Then you have the 10th Doctor, who declares “No second chances, that’s the sort of man I am” when he sends the Sycorax leader to his death. The same Doctor who told the Racnoss queen that he no longer had mercy like he used to when he drowned her children.
The turnaround itself may be simply because the Doctor finds himself with his greatest enemy who has suddenly “seen the light”, in turn causing the Doctor himself to regain some of his lost hope.
If so, that would explain a bit of the end with him saving Laszlo. Really, after all the episodes before where he’s just told someone they’re going to die and there’s nothing he could do, I fully expected him to do the “I’m sorry … so, so sorry” thing he’s been doing through his run. Instead, a flash of hope seems to overtake him, giving him the energy to do the impossible, just like he used to before the Time War.
Still, on the whole, it wasn’t a good episode. It wasn’t Love & Monsters ending bad, but I’d put it right there with the first season Aliens of London - World War Three two parter.
There were some things I liked. The other three Daleks getting bold and pissed off at Dalek Sek, finally turning on him, I liked.
There were some things I hated. The pig-men were just silly. I know they’re trying for scary, but not too scary for kids, but I’d have preferred some variant of the Robomen or Ogrons.
Just don’t get me started on the crappy science of Timelord DNA transfers through lightning rods.