Jim_O - If vB Optimise is successfully calling the templates from cache, I don't see why XCache is saying the variables are blank, unless it has a problem displaying them? (They do have characters which could break certain syntax).
Either way, if the templates are being called from cache, then they are most certainly in cache
shlomot - I've not been able to replicate on vB 3.8, what vB version are you running?
NolF - Nice suggestion, I'll see what I can do as vBlog will certainly have hook locations I can plug into