I've been playing that hunter deck for awhile, and I posted it previously. Barnes is sick and you should not replace it, it's probably the best card behind CotW.
When it 'only' brings a vanilla 1/1 out, that's a 4/5 in stats spread over two bodies. Being spread over two bodies means it's harder for your opponent to clear both of them without AoE spells, it gets added benefit from direwolf and leokk, provides extra bodies for abusive targets, etc.. and that's in the worst case scenario. When it pops out a kindly grandmother or something, it's insane and often wins the game.
There also aren't any single legendaries that would improve that list as it currently stands. Sylvanas or N'zoth are the only things that would be decent, but then you'd just want to make a nzoth hunter list and change quite a few cards (such as taking out houndmaster). I also have a nzoth hunter list I posted before and it's quite solid as well, but this one has had a slightly higher winrate. I would play the nzoth list for fun when I got bored of this one.
Now, if you just want to mess around with a new list, by all means. However, if your goal is to keep a high winrate then I'd leave that list mostly alone. Changing out some of the numbers on cards if you want to skew towards beating certain decks is fine (i.e. swapping agent horserider out for another bow, changing # of argent squires/horserider/bow/deadly shot, etc..). In fact, the list I originally copied had 1 deadly shot, I bumped it to 2 and I'm guessing you might have copied the list I posted before? Or, that change is pretty common and you just found a similar list, either way you get the idea. But most of the other changes you've talked about would dramatically change the deck.