They aren't going to make it unclearable obviously but that doesn't mean people aren't going to have SOME issues. The timewalking stuff released recently hasn't really been tuned with Legion in mind. TBC-Cata was all released in WoD before artifacts were a thing. Artifacts make them unbalanced. There were a few hard ones here and there throughout the course of the TW events. I remember Pit of Saron being interestingly tuned in WoD.