Tata - When you make the argument that your application should be allowed due to the number of registrations for the same/similar mark, you are in essence stating that the mark is fairly weak. It can work, but you can run the risk of limiting the strength of the mark in later situations (oppositions, infringement actions, licensing, etc). That being said, if you are responding to a LOC rejection, then having a weak mark over not having a registration at all may the best you can accomplish.
Regarding the specific questions you raised, it can make sense depending on the situation. Also, by raising this type of argument, it is possible to effectively show that more evidence is needed for a LOC besides a similar mark. Just be careful and not go too far.
I hope this helps.