My definition of overkill is that it could cause something else to fail. So by my definition of overkill, if it doesn't break the steering linkage, you're ok. Though having said that I use a $25 futaba 3010 servo thats about 90oz/in of torque and it gets by fine.
Check out my custom converted 8ight:
Sub 7lb, lowest CG of any 1/8 buggy