Chaos Warriors have better initiative than practically everything that doesn't have Always Strikes First, which is what makes them so OP. Saurus Warriors have about the same profile but they're not OP because they have Initiative 1, and as a result weaker enemies at least get to attack first before they are annihilated. If I had a WoC army I would do mostly Marauders to actually give my opponent a chance and just have a couple of units of Warriors as elite units. Chaos Warriors should be Special choices at any rate because they're so ridiculous.