I have to classify melee and ranged since I feel differently about them. Mainly for the no defense examples since I think melee should have a higher chance to hit and be hit than ranged.
1) You have the default To Hit value (ie no buffs), your target has no Defense value.
Melee -- chance to-hit ~80%
Ranged -- chance to-hit ~60%
2) You have the maximum possible To Hit value, and your target has no defense value.
Melee -- chance to-hit ~99%
Ranged -- chance to-hit ~95%
3) You have the default To Hit value, and your target has the maximum possible defense value.
Melee -- chance to-hit ~15%
Ranged -- chance to-hit ~10%
4) You have the maximum possible To Hit value, and your target has the maximum possible defense value.
Melee -- chance to-hit ~50%
Ranged -- chance to-hit ~50%
Basically at max to-hit and max defense it should be 50/50 but with the other examples if you stand in melee you should have a higher to-hit and higher chance of being hit.
I personally do not like to miss. That is my biggest complaint of playing lower level characters is the horrible accuracy. I also do not believe that any defense is impenetrable and therefore accuracy should always beat defense.
**All comments are based on a theoretical situation and not on current mechanics of the CoH/V game.**