A few performance comparisons exist between Dapper and (which seems to be the fastest, most popular "micro ORM tool"). As of September 2014, Entity Framework 6 (rather than 5, or 4), and Dapper are still in use.
We'll start building a large database n-tier application (database has 700 tables). Additionally, some of the queries that must be executed have a strict deadline.
Ans: I don't have the statistics, but I upgraded the performance rig to EF6. Although I can't recall the results precisely, EF6 is substantially quicker than EF-old in many instances (and about the same for the edge-cases)
Ans: Although it depends on who you ask, we believe it is worth it and prioritize speed. Expression tree parsing has an influence, and produced SQL is seldom as good as handmade SQL by a competent developer.
Ans: Yes, I've delivered four or five versions this month, I believe.
Yes, you may do that. When we first began using dapper, we did so to replace SQL to LINQ code that was having performance issues. Over time, however, this code grew, and there is now very little SQL to LINQ code left (but still some)