John, I feed a whole prey diet. The meat chunks I feed them as a meal occasionally are a treat to keep them from getting bored with the prey diet and to introduce a variety of proteins so they don't get hooked on just 1 or two. If my boys had a vote, they'd eat just chicken and quail. I don't want to risk that they will develop an allergy to either or both so they also get beef, goat, pheasant -- whatever I can find to add variety.
Because they get the meat only 1-2x week as a meal, I don't worry about balanced diet. The majority of what they eat is balanced so a couple meals a week of just meat is not an issue for them.
Servals are capable of taking down small goats and there are reports that they have done so in their native habitat in Africa. I am more concerned with variety in the cats' diet, due to dealing with IBD in one of them, than I am about the size of their native prey.
I stopped using Haretoday because of the inconsistency in quality I started seeing in my orders. I started getting a lot of freezer burned meat, packages that were torn, stuff like that. And no matter how many times I asked her to make sure she included extra ice packets, half the order would arrived completely thawed.