Here's a look at all the teams in the WCC and the composition of their rosters, including the numbers of seniors, juniors, sophomores, and freshmen they each have"

BYU---0 Seniors, 4 Juniors, 8 Sophomores, 2 Freshmen. Includes Shaw, Andrus, Nixon, and Lee. Shaw (JR) and Andrus (SO) may both get medical RS years.
Gonzaga---2 Seniors, 4 Juniors, 4 Sophomores, 5 Freshmen.
LMU---1 Senior, 2 Juniors, 4 Sophomores, 6 Freshmen.
Pacific---1 Senior, 6 Juniors, 2 Sophomores, 2 Freshmen. Senior is a graduate transfer.
Pepperdine---3 Seniors, 3 Juniors, 5 Sophomores, 6 Freshmen.
Portland---2 Seniors, 4 Juniors, 3 Sophomores, 7 Freshmen.
SMC---4 Seniors, 3 Juniors, 4 Sophomores, 4 Freshmen. 3 key starters (Landale, Naar, & Hermanson) are all seniors, as well as Neal, who is a key bench player. 2 other starters are seniors.
USD---1 Senior, 5 Juniors, 5 Sophomores, 7 Freshmen.
USF---2 Seniors, 5 Juniors, 6 Sophomores, 3 Freshmen.
Santa Clara---4 Seniors, 3 Juniors, 2 Sophomores, 4 Freshmen.

If you assign a numeric value to the experience of each roster by assigning 4 points for each senior, 3 points for each junior, 2 points for each sophomore, and 1 point for each freshman, adding all the points together and then dividing by the number of players listed on each roster you get the following results, from highest to lowest:

Pacific---2.5; Pepperdine---2.5; Saint Mary's---2.5; Santa Clara---2.5; San Francisco---2.4; Gonzaga---2.1; BYU---2.1; Portland---2.1; San Diego---2.0; LMU---1.8

But the numeric value doesn't tell the whole story since a complete roster can have a lot seniors and a lot of freshmen and will get a similar number to a team that has a lot of juniors and sophomores, but very few seniors. A more accurate value of a team's experience would be to do the same calculations as above, but just for the 5 players of each team with the most playing time. If you do that, here's what the scores are, from highest to lowest:

Saint Mary's---3.2; San Diego---3.0; Santa Clara---3.0; Gonzaga---2.8; LMU---2.6; Pacific---2.6; San Francisco---2.6; BYU---2.2; Portland---2.0; Pepperdine---1.8

Not sure what, if anything, this proves, but it is interesting. It is clear that Saint Mary's is far and away the most experienced team in the league. And BYU is one of the lesser experienced teams in the league.