I find it weird that you think trying to go ever faster is the only answer. In case you missed it, it's been well tried.
The argument you put forward or rather what you perceive is a flaw, namely 'giving them a breather in between monstering our players' is only half the story. The way it it is is our players are already being monstered so there's no net loss by a slower ptb. I already dealt with the set defence in my initial post.
Having a stationary defensive line instead of one already in motion means the time the attacking player has is greatly increased. If you force that defence to wait your attackers switch about the time imbalance.
A perfect example of how well it works is when you see a tap restart. The attack stands looking at the ref, duty bound to hold the defence 10 metres back, the attack taps the ball and passes to a player already in motion who gains 9-11 metres every single hit up. Time and time again I've watched this, even smaller players consistently make 9-10 metres.
Why? Because a set and stationary defence line NEVER jumps quickly, the tendancy is always hold straight and true. Usually the line doesn't make more than a step forward.
Anyway, all I ask is that people pay attention to what a controlled slow ptb scenario looks like in reality and as a I say the tap restart is a version of this. Of course I understand that there's no markers in the tap restart. Next time you see a restart or a defence line forced to wait(it sometimes happens with a player stung in defence and very slow to rise) pay attention to how much ground can be gained.
If our guys are getting smashed next to the last ptb and making little ground why not trade that contact point for an extra 6--7 metres?