I do love to overpower bosses (it's the only way I can overcome both my really bad coordination and luck in dice rolls). Even in my first run it was an easy tasks. In my second run I reached level 4th without even finish the Thiefling/Goblins quests.

Obviously if you aim to reckless attack the goblin bosses, the pack of gnolls, the Hag, the minotaurs, you'll get flattened in a blink of the eye.

So, no. There's no need to have an higher starting level. (And I say this as a casual player who does not strategize on wich position make the pary members take, what order to use spells, but one that run in the enemy and just start hitting, and as a player who enjoy a easy ride).