Let's put some real number to this claim about the Tribe's demise and see what we get. Using TFFRS we can see performances starting with Gibby's last year at W&M, and then move on from there. This will be a long post so if you don't want to look at the data just go to the bottom.
We'll do this by academic school year to make things simple. I chose the mile/3k/5k for indoors, and the 1500/5k/10k for outdoors because those are the distances raced at nationals (except 3k steeple which has fairly low participation). I recorded approximately the top 5-7 performances in each event to show the depth that the program had in that event. Gibby left after the 2010 track season, to be replaced by Walsh starting with the 2010 XC season. So let's see what happened...
2009-2010 school year: (Gibby's last year)
XC: 5th at nationals
Indoors: Mile - |4:08, 4:10, 4:10, 4:13, 4:13, 4:14, 4:14, 4:14|. 3k - |8:07, 8:14, 8:21, 8:25, 8:25|. 5k - |13:46, 14:23, 14:26, 14:29, 14:37|.
Outdoors: 1500 - |3:47, 3:48, 3:48, 3:50, 3:53|. 5k - |13:53, 13:54, 13:56, 14:01, 14:39|. 10k - |28:40, 29:38, 29:46, 30:08|.
2010-2011 school year: (Walsh's first year)
XC: 19th at nationals
Indoors: Mile - |4:08, 4:10, 4:10, 4:17|. 3k - |8:15, 8:16, 8:19, 8:21, 8:22|. 5k - |14:10, 14:26, 14:34, 14:39|.
Outdoors: 1500 - |3:44, 3:47, 3:50, 3:56|. 5k - |14:02, 14:18, 14:20, 14:22, 14:23, 14:27|. 10k - |29:25, 29:49, 29:55, 29:59|.
2011-2012 school year: (Athletes recruited/coached by Gibby marked with an asterisk * hereafter)
XC: 3rd at SE Regionals (breaks 14 year streak at nationals)
Indoors: Mile - |4:06*, 4:07*, 4:12*, 4:14*, 4:17*|. 3k - |8:10*, 8:10*, 8:20*, 8:20*, 8:21*, 8:23*, 8:24*|. 5k - |14:04*, 14:07*, 14:20*. 14:29*|.
Outdoors: 1500 - |3:43*, 3:48*, 3:54*, 3:57*, 3:57*|. 5k - |14:08*, 14:18*, 14:22*, 14:44*, 14:45*|. 10k - |29:28*, 29:51*, 30:43*, 30:50*|.
2012-2013 school year: (Walsh's third year)
XC: 8th at SE Regionals
Indoors: Mile - |4:07*, 4:08*, 4:19, 4:21|. 3k - |8:05*, 8:14*, 8:16*, 8:30, 8:31, 8:33|. 5k - |14:05*, 14:24*, 14:27*, 14:48, 15:06|.
Outdoors: 1500 - |3:46*, 3:51*, 3:53*, 3:54*, 3:58|. 5k - |13:55*, 14:13*, 14:13*, 14:35*, 14:40, 14:52|. 10k - |29:29*, 29:50*, 30:20*, 31:09|.
2013-2014 school year: (Walsh's fourth year)
XC: 6th at SE Regionals
Indoors: Mile - |4:17, 4:22, 4:22, 4:26|. 3k - |8:27, 8:33, 8:34, 8:34, 8:35|. 5k - |14:22, 14:43, 14:49*, 14:49, 14:57|.
Outdoors: 1500 - |3:48, 3:55, 3:56, 3:58*, 4:02|. 5k - |14:23*, 14:36, 14:38, 14:46, 14:47, 14:56|. 10k - |30:38*, 30:40, 32:11, 32:12|.
Some obvious things that stand out: As Gibby's athletes graduated/transferred the team got significantly worse. Walsh's first few recruiting classes have been significantly worse than the team used to be. I feel like four years is enough time to make a transition and get the athletes you want. It looks like there are a lot of frosh/soph right now which could bode well for the future.
Some questions that need to be asked: what the heck happened to the depth? Where did all the 10k guys go? Why did the top guys not come back for a 5th year? What the heck happened to Walsh's first recruiting class (as far as I can see not a single one has stuck around)?
Overall conclusion: Something has gone terribly wrong at this university. Whether it's administration, coaching, recruiting, or something else, it looks like a complete disaster from the performance side of things. From the above posts it looks like the athletes are having some coaching problems. Hopefully the administration can step in and make some big changes to the way things have been going. At any other big school with as good of a distance program, the coach would have been canned or left by now. Looks like the administration needs to do some research and get feedback from the current athletes.