You are plainly assuming that the most likely scenario is that "the intruder" is most likely to get violent. The fact is that most intruders, when discovered, will flee. You're also disregarding the fact that avoiding such confrontations is pretty simple. Basic security precautions like deadlocks and security screens are adequate to deter most would be home invaders. You're tying yourself in overly contrived "what if" scenarios to try to justify largely avoidable gun violence.
Lastly, you're avoiding the huge elephant in the room, i.e. being armed is not a guarantee that you will "get the drop" on the other guy. A lot of untrained, unfit Americans seem to have this strange idea that possessing a gun instantly makes you John Maclean.
And that's before we even mention the simple cost
/benefit analysis, how many people get shot accidentally, wrongfully, or self inflicted for every "successful" and "necessary" case of self defence?
Any way you cut it, "self defence" is a pretty poor justification for firearm ownership. And I say that as the owner of 7 registered weapons.