Necessary name changes? Well, yeah, there were a few. Some names needed to be changed because an english speaker would have a difficult time pronouncing it, or because it's a pun that doesn't translate, or for stupid reasons.
Gyumao comes to mind. It's VERY difficult for an english speaker to pronounce, and it's more of a title than a name anyways. Calling him The Ox King makes sense, and was necessary.
Kuririn to Krillin is another one. Kuririn is difficult to rponounce for an english speaker. Krillin isn't where I'd have gone though. My prefered romanization is "Kurillin". It's easy to pronounce, and it preserves the pun. It even comes out sounding nearly the same as the Funimation equivilent.
Saichoro to Guru - Another difficult to pronounce, difficult to remember name. I think of Guru as being more his title than his name anyways. He's Namek's Guru the same way the good half of the son of Kattats(or whatever) is Earth's Kami. Namek's religion is just set up a bit differently is all.
The Evil Dragons - Pronouncing Chinese words is very difficult for Japanese people, and perhaps moreso for English speakers. Perhaps they should have used something different, but a name change was in order.
Perhaps 1 Star Dragon or Sheng Long(instead of Shenron), 2 Star Dragon, etc.
As for difficult to translate puns...someone brought up Android 8. He's Ha-chan, right? That's the first syllable of the word for 8(his real name), with a diminutive honorific attached, much like one would do with a young girl's name to make a nickname for her. There's no real english equilivent, nor really any other way to make a diminutive form of "eight". So, while it may not sound the best, Eighter was the best Funimation could come up with, and I can't do any better
Name changes I didn't think were necessary:
Tenshinhan to Tien Shinhan. Tenshinhan isn't hard to pronounce, it's just a mouthful. Calling him "ten" for short mnay have been confusing though...
Bra to Bulla, Lunch to Launch, Dr. Frappe to Dr. Flappe, Olive to Olibu, etc. In each of these cases, they overlooked the obvious rominasation for one that makes no sense. In the case of "Bra", why is that any worse than Breifs, or Trunks?