If they were going to add this feature they should've thought it through more. To me any many people, it's repetitive, annoying, distracts from the rest of the game, and crosses the line from challenging fun to annoying hinderance, killing your beloved npcs along the way.
Here's what should have been done:
1. Make it so that instead of repetitive and mindless vampire killing, you can help the guards FIGHT BACK by training and upgrading them. If you're a vampire hunter, doesn't this make sense? This will decrease the liklihood of attack, make attacks happen outside of the gates with vampires TRYING to get in, and increases guard's chances of killing them quickly should they break in. If this is an "invasion of vampires" they should have gone all the way and let people REALLY fight back.
2. Make defenseless npcs run instead of fight using the system that worked in Oblivion, where every character has a level of courage and aggression that determines whether they fight or run. This is absent in skyrim apperently.
3. Make it so that, instead of making characters essential, important npcs can only be killed by the player, sparing them from dragons and vampires. Fallout New Vegas worked fine with no essentials. Skyrim needs SOME system however, because of all the random attacks on citizens. OR they could have made generic npcs be replaced by new ones. It doesn't make sense that no one ever moves back into houses or works at inns or shops after the previous owner dies.
But none of this was done. Bethesda really didn't think this aspect through. The beta testers allegedly complained about this, thinking it was a bug, but bethesda left this in.
Again, it's in your opinion. Unless you have a straight line into Bethesda as to what they intended for this to be, then it's all in your opinion.
And a
few Beta testers complained. By no means was it a majority, and 90% of the Beta testers enjoyed the feature.
Misrepresentation of opinion as fact is very unbecoming.

Yes, IMO the randomization math has a glitch in the coding. It has to because there's so much variation from person to person in their games. But the feature will be tweaked when the next patch arrives, and that randomization will be fixed I'd imagine. But over-all, IMO, I don't think the feature need more than a minor tweak.