DL is fine with 55-60, if you're using 15-10 JTS with it. If you want to skip JTS for other VAs, then you're talking investing up to 75 to get the same results in minimizing snap delay. 2 ticks seems to be the hard coded minimum, if your post-JTS vision is 75+, then you'll see them hit minimum the vast majority of the time.
I haven't noticed much ill effects from chopping vision super low and going with full JTS, but there is an opportunity cost there, with so many good DL VAs. Most of my recent builds look more like 63 Vis / 8 JTS, to hit 78 Vis for the delay vision roll.
What Theo said re: cov LB + safeties. I don't build them below natural 90 these days, and with VAs + zone bonuses on safeties, they're well up over 100. Probably overkill, but I do detest allowing easy scores to fake builds.