I sometimes have a tendancy to over analyse things, but this time, I'll keep things simple.
June 2009 - IM UK 70.3 - Run Split: 1:29:57
July 2009 - IM Austria - Run Split: 3:33:43
December 2009 - Mauritius ITU - Run Split (10km): 43:16
July 2010 - IM Austria - Run Split: 3:26:11
September 2010 - TriStar 111 Monaco - Run Split (10km): 40:29
October 2010 - IM Hawaii - Run Split: 3:27:22
April 2011 - IM South Africa - Run Split: 3:24:53
October 2011 - IM Hawaii - Run Split: 3:18:32
December 2011 - IM Western Australia - Run Split: 3:22:05
2009 - 1468.92 miles
2010 - 1509.18 miles
2011 - 1804.17 miles
My run improved in 2010 despite no appreciable increase in total volume over 2009. However, at Kona 2011 there was a good improvement, where between May and September that year I increased both volume and intensity, logging 920.95 miles in that 5 month period. In general, more running = faster run times, but there is of course a point of diminishing returns, although a tiny percentage of triathletes are in danger of reaching that point. Run more and run faster. The trick is getting the balance right, and that's before you've thought about integrating swim and bike training. Getting this balance right is, in my opinion, the most important role a coach plays.