lower your fps, no bot needs more than 25 fps and set everything to low, disable plugins. your system should handle 10 bots, at least, you are not even running virtual machines. my friends 2500k@stock can handle 6 bots in vmware (1vm/1bot), it was with hb but i didnt see any significant difference in between both bots in cpu load.
the cpu load is fine, im running 11 vms at the moment, 1 bot in each vm, everything on low, 25 fps and the load is about 60% on my
[email protected], so i guess i can handle about 20 vms when i lower the fps to 20 (with some more tweaks, which is pretty good). legion needs a lot of more cpu power and ram than wod, suicide instances with hb took at least 25% more load when 7.0 came out. in wod i could run 28 naxx bots with hb, 25 with nemesis. now its sth like 18@hb, 20@wrobot, but remember, im using virtual machines.
and dont forget to check for parked cores.