People always ask this, and I always reply, "It depends on your playing style."

If you like to thoughtlessly charge into combat, relying on your ability to withstand huge amounts of damage, Warrior is the starter class for you. I don't know how complementary Necromancer would be to warrior as a secondary, though I do see how vampiric touch could come in really handy. Warrior/Monk is the most common warrior build that I've seen around For PvE, I really like Elementalist because they can take out large groups of mobs quickly. For raw one-on-one combat, though, Warrior is unequaled.