Incorrect, it would simply depend on how far the defendant took it. Having one functional arm would be taken into account and if you were in a situation were you felt threatened enough to use a sword and you attacked the intruder enough so as to neutralise the threat, you are fine.
That is what is meant by 'reasonable' in our law. You can do what you like upto and including murder provided you can justify to a jury that the force you applied was neccessary. Simply put, provided you do not carry on with the attack once the threat has been removed you are fine. It's with the obvious cases where you get the shaft. Example?
Intruder enters house. He is a big fellow, carrying himself confidently. He spots you, and begins to come towards you. You shoot him with a shotgun in the legs to incapacitate him, or if you felt his presence was enough of a threat (which anyone can say

) then kill him. That can be legally justified here.
Same scenario as above, except this time he spots you and runs off. You try and shoot him, then give chase and shoot at him. In this case, you could be arrested. Why? Because once he started running away from you, the threat disappears - there is no reason to chase and shoot, other than your own revenge instincts kicking in.
I understand your views of course. The only reason I don't agree fully with the "Any intruder can be dealt with by deadly force" law is because it is much more open for abuse and allowing people to get away with murder in cases where perhaps it's not justified. Each to their own views I suppose.