There was no way the three of them would attack without any reservations and weaken themselves till they collapsed. If something like that happened, they could foresee themselves turning on one another, ambushing their "comrades".
The Nine Evil Paths had never been a single organization. There was much enmity among the various factions. Although they could join forces for the sake of benefits, once the job was done, merciless fall outs were not uncommon. It was the same for those from the Heterodox...
They would not sacrifice their lives for something like that. Since they had "comrades" and backup that would arrive soon, being a little more conservative was natural. Therefore, they would not counter Meng Qi's attacks too seriously, because their main intent was to whittle away at his strength as well as find a chance to injure him...
