That regex filter is broken and won’t catch most torrent seeding. it should be:
add comment="" name=BITTORENT regexp="^(\\x13bittorrent protocol|azver\\x01\$|\
get /scrape\\\?info_hash=|get /announce\\\?info_hash=|get /client/bitcomet/\
|GET /data\\\?fid=)|d1:ad2:id20:|\\x08'7P\\)[RP]\\r\\n"
It’s a bit of a long post, but there is a LOT of good information for solving this here: http://forum.mikrotik.com/t/how-block-connection-of-p2p/18495/1