Right, variance of wait time -- not just the mean -- is definitely a(n anti-)desideratum, for exactly the reason you gave[1]. I don't know how much emphasis academic queueing theory puts on this though.

[1] To put it another way, you can assume entrants plan for the line to take less than the 95th (or whatever) percentile time; the lower you get this figure, they better they can allocate their time for other tasks.