Have thought a lot about the EC since stumbling into this discussion last night. There is no defense, logical or otherwise, necessary. The onus to defend or prosecute is on those who wish to change the current system.
To answer your second question: just like checks and balances are inherent in our system to ward against tyranny, different pathways to government leadership exist as safeguards from tyranny. Some positions are elected by popular vote, some positions are appointed, and one is elected by appointed Electors. Senators were originally appointed (should still be, imo). Supreme court justices are appointed. There is wisdom in removing the "majority rule" approach as power is condensed. Representatives, have less individual power than Senators, Justices, or the President. Majority rule for Representatives is less dangerous than majority rule for President. Furthermore, the design gives voice to all the governed. The people by Representatives. The states by Senators. And the Federal by the President.