It is just impossible to fight above or below your level because everything is level dependent. Everything.
Not only has the character his hitpoints increased (base * level) but also his weapon (base damage * weapon level) and his armor (base * armor level) are increased. That is simply to much per level.
I have not found that to be the case. Below level? You can always fight them. Above level encounters I've done several +2 levels, it can get tricky for sure and not a guaranteed win, thinking I've beat at least one +3 above. Pretty common though for level based RPG's staying near level, otherwise someone can make a claim that is unrealistic that my level 4 team can beat level 7 baddies.
About linearity, you have to be at a certain point sure, but it's not I have to be 6 to take on their 6's. Tactics matter. So lets say I can take on 7's and 8 baddies at level 6. Well now I have 8 levels that I can play against 1-8, why is that linear?
We also know the other side of this argument, it reached its pinnacle in Bethesda's Oblivion and it got lambasted where all encounters were scaled to you. Everything was the same fight, you could go anywhere without risk, etc etc.
There is no overall win on this one, we've been talking in circles as a gaming community for year. We can just hope whatever the designers make it will be well balanced and fun. Old school says I can't go anywhere I choose, I will hit a high level mob that forces me to go look elsewhere to gain strength. Otherwise no area is sacred, you can just go the straightest path to the end of the game.
