I experimented with 2x AtB1 with 2x Purple & 1 Blue Technician DOFF. Figured I'd get BOFF skill CDs melting away but that wasn't the case for me. Granted it wasn't a very scientific approach but just a gut feel vs. my previous long term build. For example, EPtS didn't get down to 15 sec until 3 AtB activations. Also it seemed the lower the number of seconds remaining on CD (i.e., 12 secs vs 30) the less the reduction was. Almost like the CD reduction was a percentage of the remaining CD rather than a percentage of the total skill CD.
So while I was expecting something more to write home about, I'm afraid I will stick to my 2xTT and 3 Damage Control DOFFS for now. I know the Techs work on all BOFF skills but TT & EPtX are key to me.