Folks can teleport, throw blasts of flame all day, fire two arrows at rapid speed, cure wounds all day, be expected to have platemail, etc. at the very start.
Thanks for providing examples -- this helps considerably. I think they could each benefit from their own analysis:
* Folks can teleport: The only 1st-level characters likely to teleport are swordmages and eladrin. As swordmages are peculiar to the Forgotten Realms, I think we can put them aside for the moment, which leaves us with the eladrin.
Non-humans are a bit tricky to handle with a set-up like this, no doubt about it. I'm inclined to think this was true in earlier editions -- "We're just some kids from the farm... including that two-centuries-old elf who's tagging along with us." It can be done, sure. But I think within the structure of the story, the eladrin's ability to teleport is just one of the concerns, and not necessarily at the top of the list.
I think it's sensible enough with a set-up like this to suggest to the players that they stick to humans, or to ask them to come up with some reason why the dwarf is there in the first place.
* Throw blasts of flame all day: Yep. I see this as a matter of degree -- if a 1st-level player can cast Colour Spray, then it's a matter of degree as to whether he can cast that once a month, once a day, once an hour, or once a second. If the story can accept he can do it at all, then the rest is detail.
I wouldn't rule out, for this sort of story, to ask the players to stick to the martial classes, or to ask them to come up with some reason a spell-slinger is planting turnips along with everyone else.
* Fire two arrows at rapid speed: This isn't something I'm likely to find problematic. If I can accept that a guy can fire an arrow into combat every six seconds, it seems like I can accept he can hurry that up to once every three seconds. It's quick, sure, but I think there's enough room in the abstraction of the story to allow for it.
* Cure wounds all day: This isn't really quite true, but that's alright. If one can accept divine intervention in the first place, then it doesn't seem like such an intolerable stretch, to me. Hit points are already such an abstraction in the story that I don't find it especially problematic for that one really pious guy to be able to pray for me every hour and then I feel better.
* Expected to have platemail: This is a bit sticky, but changing the starting gold of 1st-level PCs is such a slight change that I hesitate to call it a house rule as such. Alternatively, it's certainly within the scope of the DM's discretion to declare that some equipment is just not available to the PCs starting in this particular scenario.
There are issues here, but they don't strike me as anything that sprang up between 3E and 4E. If your story could handle a 3E elven wizard among your turnip farmers, I think it can handle the 4E version just as handily. If, for some good reasons, the PC elven wizard wasn't ever part of this scenario, then that's fine too.
Cheers,
Roger