Regarding the two witnesses in Rev. 11, I believe that they ARE the 144,000 that are sealed from the Northern and Southern Tribes of Israel that were divided in the OT.  Two people, alone, cannot possibly encompass the world with the truth of the Word of God during this 3 1/2 years.  Here is a link with a biblical explanation that seems to fit the description of the "two olive trees and the two candlesticks" which defines these witnesses:

http://www.herealittletherealittle.net/index.cfm?page_name=2-Witnesses-in-Revelation

This is a better, and updated, version of the similar article from 2010.  It makes perfect sense.

YsiC,
Arlene