Going for potency, tenacity, survivability and perhaps some offense seems obvious but is it at all useful to go for a bit of speed on secondaries or should you avoid speed altogether?
I guess it would depend on how the 100% tm gain works exactly:
If this means that at whatever amount of tm you have at the moment relentless barrage tm gain kicks in, your tm bar is filled up to 100%tm and you start at 0 + your usual tm gain next turn, than speed would be of no use. Being slow, relentless barrage would trigger before you can make a regular turn.
If however the excess tm after gaining the 100% is added to your regular tm gain, speed would be useful.