We have been fighting SBH's in renegade for 12 years without a problem. The sprinting is much more an advantage for the defending team who can get to the nukes much quicker, than it is for the attacking team.
The real nerf for the defending team is that it cannot use the PT from the outside of the building anymore. But TBH, strangely enough I have not missed that a lot in RenegadeX, thanks to the sprint.
About mining: in Ren as well, the mine limit was 30. You need to make choices as to which doors you mine and how many mines at which door. At major advantage to the defending team in RenX is the mine counter that's displayed constantly! Put 1 or 2 mine at each door and 4 at the doors you cannot see. Keep track of the mine counter while defending.
If you cannot counter SBH's in Ren / RenX, then I'm afraid it's more due to the GDI gameplay than due to the SBH being "OP".