Yes, 100%+ in a single resist should be achievable, but with dedication, specific talents, skills, etc. I'm not even talking 100% though, even the ease of achieving 50% resist in most resists is a problem. That's halving the damage of mages and elements.
Every item slot can potentially receive a 30/20/10% resist combo (and quite often, too). It's easy to extrapolate from act 1 to see that by act 2 if you spend your time gearing up you'll be sitting at 50/60%+ resists (nevermind leadership). If they try to balance around these kinds of resists, people who don't gear up with massive resists will get annihilated.
@Baardvark
Do it yourself. The game is perfect with this. If you dont like something you can change it yourself from the files. I think the game drops trash items and i feel super weak, no matter my level. Just because you like to feel like trash ingame, doesnt mean we all want that. No offence bro.
Well, I've already changed it in my mod for next version. I don't want to feel like "trash," but I don't want uber-resists handed to me. I'll agree that other than massive resists, loot is fairly unimpressive overall. Not necessarily bad, but boring and inconsistent. I'd rather they make loot more interesting than stacking massive resists on everything.