Actually...while my main is a Paladin, I far more enjoy tanking on my Warrior for bosses and even trash. It's involved and actually has far more options to kick casts, debuff whole groups and stun better and more often. Is that
really needed for trash? No...but it is fun and feels cool. On my paladin I can safely tap 2 buttons occasionally whenever they're up and never have to tab around and watch what I'm doing...but that's boring as hell.
Warriors can AE tank just fine but there's one pretty key downside to it: you have to do more (in terms of hitting more buttons, looking where you are, tabbing about etc) and you have to make sure your DPS aren't retarded. For me, that is actually a massive break from paladin tanking (which I personally find boring, moreso because I've done it far longer than anything) and it leaves me with a mild sense of accomplishment to have not failed. When I see a large group of trash with 5 sunders, demo shout, tclap and all of it hitting me...I feel good. When I can charge around, kick heals, intervene and intercept back somewhere else...it's amazing.
So really in summary you can pretty much do as good a job as a paladin on trash (or a DK or a bear). If you aren't doing it yourself, you just need to mash more buttons, tab more and pay a lot of attention. That is the FUN part of the class. If you don't like doing it, then you are playing the wrong class. If you don't like managing runes, you shouldn't be a DK. If you don't like having to watch dot timers, you shouldn't be an Affliction warlock. Don't like totems? Don't be a Shaman. There's several fundamental elements that go hand in hand with playing a class or spec and for prot warriors, it is being very busy on big trash pulls.
There is a huge difference between 'easy' and 'good'. All tanks can be good at AE tanking, it's just some are more simple than others. As someone else said, it doesn't matter if you're 130% over DPS or 170%. What you need to learn (and what a lot of newer tanks lack) is to tell DPS to
PAY ATTENTION. If you are spamming every ability and have no GCDs left and they are still pulling off you, it is their own fault for doing something they shouldn't and dying. Did people DPS like that in Vanilla? No. Did they do it in BC? Hell no. They seem to believe that aggro falls from the sky and keeps them alive while they spam Seeds of Corruption as soon as they see you heroic throw. Let them die a few times and see if they keep doing it
Also: I like tanking trash. Does it make or break warriors as a class? No. I like tanking it. Some people hate it (I do on my paladin).