What can I do to prevent possible gradual erosion on this small slope
If the pavers were installed properly--and it looks like they were--the edge banding should be staked into the ground much deeper than 6". So, structurally, I think there is nothing to worry about.

Now, aesthetically, it does seem a little wonky. But we can't see the larger picture here. 

That said, if you are worried about a bit of erosion over time, I'd suggest removing the mulch up to the pavers and plant grass there. The grass will help stop any erosion over that small of a slope.