You can get Warlock/Hunter/Titan kills in the crucible if you are near a teammate. You can not get Kills AS a Warlock/Hunter/Titan if a teammate is near you. For example: you're a warlock, and you're friend is a Titan next to you. Your fellow Titan just killed someone, but you will not see your Kills as a Titan go up. However, your fellow Titan just killed a Hunter. You WILL see your Hunter kills go up, even though you didn't kill the Hunter. Make sense? Sorry I didn't respond earlier.