razor talent lvl priority?

hi i leveled razors auto attacks to 10 and wonder what i should level next? the thunderclaw gets nice dmg % increase but i have no electric dmg amplifiers (I am full phys dmg) just for reference my auto attacks hit for 10-20k while my thunderclaw hits for 3-8k... so i wonder if i should level his ultimate but he gets only 1% attack speed per level, so what skill is worth more? or should i keep the mats and stop lvl the talents at lvl 6 and instead maybe give some talent levels to my c6 noelle?