In general, is a Thief required?

For most of all the IE games. If I wanted to solo the game as say, a druid or something like that, would I be able play the game without thieving skills (detect/remove traps and lockpicking) or the knock mage spell, or would I be missing out on good loot from chests / locked areas that would be game changing? Just wondering what you guys thought about it. I really wanted to try to solo the game as a druid or something similar. I just don't know how vital a thief is to the party, especially when you don't have access to the mage spell counterparts to their abilities.