15,000-20,000 Transaction Logs per day

I have an Exchange 2010 DAG (over a WAN) who's transaction logs seem to be growing rapidly each day. They are getting backed up and it's VSS aware. But it's taking days to truncate the logs because they are just being generated so quickly. I have about 100 users in this database and while volume is high, 15,000 - 20,000 per day (and growing) .log files does not seem right. What should I check?