There is another thing at play here, seeing them have to actually train as well to accrue strength means that they would get adjusted to wielding and using their strength and speed. While a boon may be helpful in certain situations, it could also be a detriment. Using your speed example, if you were to suddenly be faster then your swings would take less time but if you're used to moving at a certain speed then you'll more than likely end up overcompensating and swinging too early resulting in an opening to be killed. You'd have to in combat adjust to the new effects and then adjust again after it wears off which is not ideal, especially if there is downtime between the buffs.
Depending on how the buffs actually work, 'Talker' could be pretty powerful. Are they %? Flat amounts? They aren't really giving us anything to go on other than this kid kept up with that scary old man in 1v1.
@Liu Well I've read the novel and all I can say is that it makes sense due to how their world works, there's a reason they're considered useless despite being specialized buffers. And note that it's the weakest 'combat' job.
I get killing an enemy and dying anyway because you slowly bleed out or something, but damn, how do you land a killing blow when you're just a torso with a single arm?