I preferred when we were the Legion of Erratablight, myself.
Legion got substantially toned down in the edition change. Not to mention they were so godly during the Field Test that the collective moaning from other players nearly birthed a Chaos God of Despair. Oh, Field Test Vayl and Bow-Cannon Lylyth...how I miss you
It's not a single unit or choice that makes an army good - it's the overall interaction of the chosen forces. You can't just select things at random and expect a solid result.
Think of army building (in any game, really) as baking a cake - there are a lot of ingredients and a lot of potential flavors, but it's up to you to make sure the end product is to your tastes