Specifically, both IT and TC change the hardness of blocks. When they are added together, the breakspeed for TC doesn't work anymore, going to the vanilla break speed. I would really like to see this fixed, as it ruins the balancing/difficulty effects of both mods. And if you do fix it, It would be extremely appreciated if you fixed it in the 1.7.10 version of TC, since that is the version most updated modpacks