This I can imagine working quite nicely..
Harlequins advance being all shadowy /w not being able to be targeted.. then with a 6" gap (to avoid scatter spamming hits on those 5++ harlies) infront of the wraithguard lending a 4+ cover (so give the warlock somthing other than conceal.. enhance is the only other viable option) and then the wraithguard dotted through/behind those wraithguard getting another 4+ cover save?
Perhaps one guard with a rear-guard rangers team.
The other two stationary infiltrating rangers are met/past by that moving block of doom. Harlies & another wraithlord could go off on another flank (shadowseer = psyker

)
Suggestions : Doom. With that much rending.. a 10man harlie squad (or two?!) could put a serious dent in even a 10man termie squad or some other manner of death.
Bout it.