I find myself using 3DC more and more, and find it very effective for both the 3x ST or AML/(C)/R + ST attacks more often used nowadays. For wing players I add DL/DR in the DML/R positions, for more central attacking formations (Narrow Diamond, et al) I add a DMC.

More often than not, I am playing 3DC-DML/R-2MC-AML/R-ST Butterfly formation, I can usually overcome a 4-5-1V by using Butterfly and playing through the middle (!). 4-3-3 and 4-1-2-1-2 Narrow Diamond are countered using 3DC-DMC-3MC-AML/R-ST, again a 3DC formation. I have a MC/AMC and he will be pushed up to AMC if I need to play a more offensive formation to put a weak opponent to the sword or rescue a losing situation.