the town level youre in depends on the level of armor the blacksmith can craft.
as you can see, i'm in a level 45 town, in which the blacksmith can craft level 45 armor (the legendary hat is selected) with these items;
https://puu.sh/wzOHn/a3274a725a.PNG
the cost for legendary gear is quite high, which is why i recommend you wait until youre higher level because you dont need it asap.
its not more exp to work as a group its twice as many drops, theres a specific quest (ive had 2 so far, on the second one) that requires you to go with someone and finish an insane dungeon.
usualyl those dungeons are harder than other insane dungeons, however i can solo it so it kidna sucks no1 is willing to do it with me...