I really do not know what you are talking about or how it is relevant to the discussion. This just sounds like a personal rant.
I disagree. I know for a fact that it can slow down combat. We (my group) likes armor to have DR combat and we add it to every edition we've played (1e, 4e, & 5e). However, the issue has been that it did indeed slow down combat - always. We didn't really come up with a good solution to minimize the effect until 4e came along and two things led us to a solution:
- 4e combats could be very long, see we looked for many new ways to speed up combat, that made us look hard at DR again.
- The bloodied condition, That concept was a revelation for us and gave us the idea to minimize the impact of adding DR to armor.