You should do all areas and side quests. The extra levels that the experience give you, plus the gold and items, will help as you progress through the game.
It's normal. It's up to you if you want to do Colossus Blvd. I think you should do it because of these reasons. !. You can get the Smith 2. You need it to get the History Books 3. You will need it later to get the obsiden chest and Briskbreeze. 4. There is a secret shop in there. 5. There are pet drops in there.
Also, at some point Gloria will have a series of quests that creates a full set of clothes for you. Depending on your gear, this is worth doing as it is pretty much the best you can get before going into Krok.
Yes, it is very normal. But Colossus Boulevard is more of a training street than a top priority route. Krokotopia is a very important world as in it involves you into the Order of the Fang and once finished enables you to go to Marleybone, home of the canines. 8)
