When I learnt ～ほど～ない grammar, I found examples with 他に as follows. For me, the presence of 他に seems to be wasteful because
私ほどハンサムな人はいない。There is none as handsome as I.
私ほどハンサムな人は他にいない。There is no other person as handsome as I.
logically "none" in this context should be enough to represent other persons excluding me.
Is 他に essential in ～ほど～ない grammar?
Essentially these two statements are the same. Both are of the meaning that there is "No one more handsome than me"
私{わたし}ほどハンサムな人はいない。
私{わたし}ほどハンサムな人は他{ほか}にいない。
Basically what you are doing with the second sentence is "emphasizing" or 「強調{きょうちょう}」in Japanese, that there is no one else as handsome as you.
It sort of makes you as if you are the bees knees and full of yourself. Not disregarding that saying that you are the most handsome in the first place suggests that you are pretty confident in yourself (I am not saying that what you are , just in regards to the meaning of the question.)
これほど美味{おい}しいパンはない。There is no bread a nice as this.
これほど美味{おい}しいパンは他{ほか}にない。There is no other bread as nice as this.
Same deal in this case as well.
Essentially, 「他{ほか}に」 in conjunction with「～ほど～ない」just emphasizes what you are trying to convey. I can't think of a case where it would change the meaning greatly.
