Are you sure they round up to the nearest second? I remember reading that they don't accept anything past 1 decimal place, which would make no sense if they round up to the nearest second (assuming my memory and the post I read were both correct). Also, I noticed a large difference going from 3 seconds to 2.5 on my macros, but it could just be placebo.

I craft with macros all the time, and never have lag/missed step issues. I have a solid cable connection, and I don't synth in laggy areas where I have to wait for NPC's to load up.

Especially on 1 and 2 star recipes, the early touches without Ingenuity aren't worth wasting CP on Standard or Advanced touch. That extra CP is better used buffing your BB, either through more steps (Manipulation instead of WN, etc) or less Synthesis steps (1x/2x Standard instead of 2x/3x Careful) This is the same reason Hasty Touch spam is so effective.