Just to elaborate on the profession difference exp:
Warrior, Ranger, and Monk primary or secondary offers 2 quests each, both of each grant 250exp. Example, W/Mo will have 4 profession specific quests for a total of 1,000exp.
Necromancer also has 2 quests, however one gives 250exp and the second gives 500exp. This makes any primary or secondary Necromancer able to get 750exp instead of the above 500exp for both quests tied to a profession.
Elementalist and Mesmer both only offer a single quest, for 250exp.
So to tie it into the chart, You now see why a N/W would get 1,250exp (750exp from N, and 500exp from W) versus what an E/Me would get (250exp from E and 250exp from Me). Thus making a 750exp total difference in quest rewards alone.
Considering it takes 11,000exp to get from 16 to 17, 750exp is a nice chunk.