Are the enemy levels scaled to match your own?

Yes they are scaled, but each instance is tuned in a way that not every encounter is too hard, some of them are even of a lower difficulty. In my opinion, you should level up all your party members, so you won't have any problems later.

Yes but I also think it depends on the difficulty you're playing on.

Yes, it would appear to be so, due to game-balancing design decisions on the part of the game-maker to deter exploits of experience glitches. (In other words, players who attempt to use these glitches to level-up prematurely without regard to the other factors that determine how powerful the party is, namely loot and gear, will suffer enemies that are, stats-wise, more formidable.)

However, the scaling largely only affects the stats of enemies. Their versatility in combat and their AI scripts are largely unchanged. If you can develop your party to have skills and abilities for any comer, you won't be getting the butts of your party members kicked around so much as those of parties whose controlling player had resorted to experience exploits.

Yes the enemy levels are scaled to match your own except Bosses