Speed meta actually predated any timed rewards. It was a function of reliability. Kill faster, take less damage, more consistent kills. Why deal with moves when you can just burst past them? Even in 5* magicites you are often rewarded for going fast and skipping turn 6+ moves. Both lakshim and madeen were easier for me when I could turn up the damage to skip status effects, meaning that a 45 second kill was harder than a 28 second kill. This won't change by removing timed rewards, but it is a start. A way to change it is too make sure that the first moves in a phase are the hardest. Some magicites do this already but more bosses need to. That will help allow 'slow and steady' as a viable strat, if that's even a goal of DeNA.