This depends on which unit you’re using GLR on because some of them don’t actually need Time’s Pulse 4 to keep GLR up constantly, but I’ll explain.

The simple answer is that some units really need Time’s Pulse 4 to constantly keep GLR charged, though it goes a bit more in depth. Damage reduction doesn’t stack additively, it stacks multiplicatively. Each time you add another layer of DR%, it’s giving you less and lees bang for your buck. That’s called diminishing returns.

Stacking a billion different methods of DR doesn’t really amount to much because most of the time, having two sources of it is more than enough. Maybe that’s why a lot of people recommend not running Spd Smoke. It’s not that it’s a horrible combination or anything, but the diminishing returns are rather off putting when you could be using a different C skill like Time’s Pulse which really helps with the upkeep of Godlike Reflexes.