The little bit of toughness just means it could have gone longer.
It is very common for the tip of the flat to overcook, being the thinnest part of the meat. The center if the flat is always where the best slices are. I generally just cut off that first 1/2 inch to an inch triangular bit off the point before slicing and cast it aside if its really dried out or even charred.
If you really want to salvage that little piece, you have options. One great thing about bbq is that your options seem limitless. As soon as you think there are only so many ways to do something, you find out about other ways.
You could cook the point and the flat separately so that the point cooks more evenly throughout. You could also leave it whole and try foiling or using a pan, but even then that little bit still tends to get overcooked.
Also, you could flip that fat cap. When I used to cook on my offset, I cooked fat cap up. Not everyone agrees about the fat cap though, and probably never will.
Also, when picking out your brisket, look for thick flats. The thinner ones tend to have even more waste at the thin end..which makes sense if you think about it.