I have recently some how got 3 of the same 5 star covers from bonus heroes and I usually sale them because I am not even really that high in the 4 stars. Will 1 unleveled multi covered 5 star really hurt pve scaling?
The question isn’t really where you are in the 4*, but where you are in the 3*. If you have enough 3* champed that you have 2-3 boosted champs in every event, you won’t see any change in scaling at all. If you have fewer than that, you might see a small effect.
I was just starting the 3* transition when 5* heroes became a thing, and it did impact me for a short time, but as I ended up with more champed 3* the impact was overwhelmed by the impact of having boosted 3* champs, and since boosted 3* champs can do just fine in PVE, it wasn’t an issue.
Hope that helps!