That sounds good in theory, especially if we are talking about an MMO or at least an online game that you can go in with a team, but in a single-player game, you would be limiting content. That's generally not something Bethesda does.
It's something they should do, what's the point in an RPG if there is no replayability, limiting content for the choices you make means there are stuff left to do when you start a new character.
Being able to do everything made me not want to replay Oblivion, no point to it, all I could do was use a different skill-set and race but the game was still exactly the same.
Thiefs are usually very agile and therefore could easily just dodge a dragons attacks.
My mind wandered to Elder Scrolls V: AniméRym.
(Could we have some CP9 skywalk too?)
If they didn't find a way for all classes to be able to deal with equal problems, if the only solution was to become a warrior- THAT would be simplifying. The ability to create different routes to one solution is a far more complex design.
No, that means that
you can't accept that you cannot deal with a problem, so
you choose to become a warrior simply so you can take them down.
It shouldn't be an equal world, it's an RPG for Willis' sake, depending on the character you craft you will be good in some areas and horrible in others.
If your character is not fit for fighting a dragon then it's a choice
you've made, this character will be better in areas that your dragon killer character will not.
We already have Dragon Shouts right? So what about some Dragon Shouts for characters not fit to fight dragons that allows them to evade or escape them?
Just cause there's dragons in the game doesn't mean that every one should be able to kill them.
You choose whether you want to steer your character towards a path that allows him/her to be able to defeat them.
It doesn't mean you
have to become the same character over and over, learn to accept that certain characters have certain flaws preventing them from achieving feats that others can.
[edit]
BUT! The main quest should be completable for any and all kinds of characters, so if you have to fight a dragon or two during the main quest and it's not an option to run away then allow for something around you to be used as weapons, for a thief character you could have some pillar that you could try to push over them, or maybe a chandeler(?) that you can shoot with a bow to drop on it's head.
Or yknow, simply don't design the game so that a dragon fight is unavoidable. :shrug:
As for Alduin or whatever his name is; I guess these characters will need to use strategy, using Dragon Shouts only while evading the dragon.
[edit2]
Think about it like this: The more content you're locked out of cause of the way you designed your character the more content you have for subsequent playthroughs.
Doesn't mean there won't be anything to do, just means that you will occasionally find quests that you cannot finish or even start.
Or well, you might be able to finish the quest, but maybe not the way you wanted to finish it.
(Like how in New Vegas if you don't have a good Speech then certain quests can roll down a bad path, can still finish them, but not the way I wanted to.)