Hi Phil W
Nice animation and lighting.
if you have a couple of figures replicated, and use an NLA clip, then you can adjust the timing in the NLA parameters for each clip, ..
so you could have the clip speed set to 1.00 , on one figure , and set the speed to 0.75 on another figures clip, to make it a little bit slower.
if you have more figures in the replicator, each one using the same clip but at a slightly different speed, that will give you greater variation.
or you can use the same NLA clip many times in the track at different speeds, instead of just looping it. so some clips could play slightly slower or faster than normal speed.
Hope it helps