A leader is definitely needed, but it doesn't have to be steel. Actually the most popular leaders today are made of fluorocarbon. DO NOT use anything less than 100 lb., you will get bit off sooner or later.
Personally, I use Stealth Tackle 130 and 150 lb. Fluorocarbon Leaders. I only used 2 different leaders all year last year, a 130 lb on my all around rod, and a 150 lb on my big rubber rod.
Also, use a good snap, I like the Stay-loks. Never had one of those fail on me. One last thing, please stay away from Musky Bill's Leaders, they are absolute junk in my opinion. They failed me on 2 different occasions, both times I lost an expensive bait too.